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of the differentiation of homoplastids into the lowest commencement, can continue inriefinitely with or without heteroplastids ; in Pandorina the cells are still all alike modification (specific changes in the germ-plasm or the and all perform the same functions, in Volvox occur monoplastids), it is a cyclical activity of organic material somantic and germinal cells, and in the latter case we devoid of any intrinsic momentum which would lead to shoald expect to find the commencement of natural death. its cessation, just as the motion of the planets contains no Recent researches of Dr. Klein ("Morphologische und intrinsic momentum which would lead to its cessation, biologische Studien uber die Gattung. Volvox," Jahrb. although it has had a commencement and will some day, wisk. Botan., xx., 1889) show that this is actually the through the operation of extrinsic forces, have an end. case; as soon as the germ-cells are ripe and emerge Prof. Vines says later: "I understand Prof. Weismann from the sphere, the ciliated somatic cells begin to shrivel to imply that his theory of heredity is not-like, for up, and die in one or two days. This is the more interest instance, Darwin's theory of pangenesis-a provisional ing, as the somatic are also the nutritive cells; for, though or purely formal solution of the question, but one which the germ-cells also possess chlorophyll, the rapid growth is applicable to every detail of embryogeny, as well as to of the latter (which attain an enormous size in Volvox) is the more general phenomena of heredity and variation.” only possible by the supply of nourishment from the I have, as a matter of fact, designated Darwin's pangenesis somatic cells. The latter are so constituted that they as a “purely formal” solution of the question, but should assimilate, but cannot grow larger when once the sphere like here to give a slight explanation of the expression, as has reached its definite size; they transfer the nourishment I fear that not only Prof. Vines, but also many other which they derive from the decomposition of carbon readers of my essays, have misunderstood me. On the droxide, &c., to the germinal cells by means of fine one hand, I am afraid that they see in my words a definite pseudopodia; and themselves wither when once the reproach against Darwin for his theory of pangenesis, of germs are ripe. In this case adaptation to the nutrition which I had not the remotest intention; and on the other, of the germinal cells might well have accelerated the that they incline to charge me with too great an affection introduction of a natural death of the somatic cells, the for my own theory. capacity for considerable assimilation combined with a I believe there are two kinds of theory ; one may term drain on their nutrition may have led after a certain them the "real" and the “ideal”; practically they are time to stoppage of the process of assimilation and to rarely sharply to be discriminated both often occur in death. To me, the idea that modification of the living one and the same theory, but should be conceived of matter may have been connected with loss of immortality separately. The “ideal” theories attempt to render condoes not appear more unlikely or more difficult than the ceivable the phenomena to be explained by an arbitrarily generally received view of the gradual differentiation of accepted principle, apart from the question whether the the somatic cells in the course of phylogeny into their principle itself possesses any grain of truth or not; they various species of digestive, secretive, motile, and nervous seek only to show that there are hypotheses on which the cells. An immortal unalterable living substance does not phenomena in question become comprehensible. “Real” exist, but only immortal forms of activity of organized theories do not make hypotheses at pleasure, but strive matter.

to construct such as have some degree of probability; I maintain, therefore, in its entirety, my original state- they desire to give not a formal, but, if possible, the right dent, that monoplastids and the germ-cells of higher explanation. Sir William Thomson in endeavouring to forms have no natural death. I do not know how this make clear the dispersion of rays of light, never believed in can to-day be better expressed than by saying that these the remotest degree that such molecules as he pictured liring units possess a real and actual immortality as really existed, but desired merely to show that there were against the imaginary ideal immortality of the Greek hypotheses on which the phenomena of dispersion were gods. If death from internal causes does not exist for comprehensible. Darwin's pangenesis was originally inthem, one may yet say with certainty that the fatal hour tended in this sense, and was by him termed a "prowill one day strike for them all, not from internal causes, visional” hypothesis, although in later years he may have but because the external conditions for the constant attributed to it the weight of a real theory. To me his "gemrenewal of vital activity will some day cease. The mules" are a pure invention, an invention in no way correphysicists prophesy that the circulation of water on the sponding to the actual facts, but showing what hypotheses globe will end, not from any alteration in the qualities of must be made in order to explain the phenomena of water, but because external conditions will render this heredity. Are, however, such ideal theories worthless ? form of motion of aqueous particles impossible.

Certainly not. They are often the first and essential step Prof. Vines then attacks my view of embryogeny. He towards the understanding of complicated phenomena, and finds it " not a little remarkable that Prof. Weismann lay the foundation for the gradual erection of a real theory. should not have offered any suggestion as to the concep- It would perhaps never have occurred to me to deny tion which he has formed of the mode in which the con- the inheritance of acquired characters, had not Darwin's version of germ-plasm into somatoplasm can take place, pangenesis shown me that the matter was only explicable considering that this assumption is the key to his whole on an hypothesis so difficult to conceive, as that of the position" He sees here the same difficulty as in the giving off, circulation, and reassemblage of gemmules. I phyletic development, and says: “There is really no do not even now maintain that Darwin's pangenesis cannot other criticism to be made on an unsupported assumption possibly contain a kernel of truth ; De Vries ("Intrasuch as this, than to say that it involves a contradiction cellulare Pangenesis,” Jena, 1889) has shown in a recent in terms." He means by this that the eternal cannot and most interesting memoir that the ideal impossible praes into the finite, as must be the case if the pangenesis may be transformed into a real and possible Immortal germ-cell grow into the mortal soma. At one by means of certain profound modifications; he acthe bottom of this objection lies the same confusion cepts my view that acquired (somatogenic) modifications between immortality and eternity which has already been cannot be transmitted,

and thereby puts on one side just made clear, I do not wish to reproach Prof. Vines with that part of Darwin's theory which has always appeared thats obscurity, as I felt the same objection myself for to me to lie beyond the pale of reality-namely, the circulamany years, and could not at once discover the reply to tion, &c., of the gemmules. The future will show whether it; on the contrary, I am indebted to him for the oppor- his view of modified gemmules or my hypothesis is the tunity to express myself on the point. Up to this time best explanation of the facts of heredity. we have had no scientific conception of immortality ; if In any case, I am far from assuming that I have settled thus be acrepted, the significance of immortality is not the whole question of heredity ; I have undertaken relife without beginning or end, but life which, after its first searches on some of the more important parts of the

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problem, and have thus been compelled to formulate character upon the originally indifferent cell-mass. From some fundamental principles for the explanation of the then onwards, I no longer designated the cells of the body phenomena; but no one can be more convinced than I simply as "somatoplasm," but distinguished, on the one how far we are from a definite and complete explanation, hand, the idioplasm or "Anlagen-plasma "oi the nucles not only of “every detail," but also of "the more general from the cell-body or “Cytoplasma," and, on the other, phenomena.” My endeavour was to put forth a real, in the idioplasm of the ovum-nucleus from that of that place of the previous ideal, theory; and on this ground Isomatic cell-nucleus ; I also for the future applied "geri took pains to make only such suppositions as might pos- plasm” to the nuclear idioplasm of ovum and spermato sibly correspond to actual facts. There certainly is a zoon, and" somatic idioplasm" to that of the body-cells material carrier of heredity in the ovum ; it certainly can (e.g. p. 184). The embryogenesis rests, according to my be transported from nucleus to nucleus; it certainly can | idea, on alterations in the nuclear idioplasına of the orum. be modified in the process, or can remain the same; and or "germ-plasm"; on p. 186, et seqq., is pictured the way in even the supposition that it is able to stamp its own cha- which the nuclear idioplasm is halved in the first cellracter on the cell contains nothing which seems to us impos- division, undergoing regular alterations of its substance in sible and non-existent; on the contrary, we are able now to such a way that neither half contains all the hereditary state that it is so, even if we do not understand in what tendencies, but the one daughter-nuclens has those al wise it happens. My hypothesis relative to the quiescent the ectoblast, the other those of the entoblast; the whole state of germ-plasma also rests on a basis of fact ; we remaining embryogenesis rests on a continuation of this know that ancestral characteristics may be transmitted process of regular alterations of the idioplasma. Each in a latent condition, and that the process of transmis- fresh cell-division sorts out tendencies which were mixed sion is bound up with a substance, the idioplasma ; there in the nucleus of the mother-cell, until the complete mass must therefore actually be an inactive stage of idioplasma. of embryonic cells is formed, each with a nuclear idio

If it could be shown that upon such principles an ex- plasm which stamps its specific histological character on planation of heredity is attainable, we should have made the cell. a distinct advance upon the ideal theory of pangenesis I really do not understand how Prof. Vines can find such which is founded on unreal hypotheses. Possibly it is remarkable difficulties in this idea. The appearance a upon the path which I have opened up that we shall the sexual cells generally occurs late in the embryogeny. gradually attain a satisfactory solution of the numerous in order, then, to preserve the continuity of germ-plasma questions at issue ; possibly further research will show from one generation to the next, I propound the hypothat it is not the right path, and must be abandoned ; no thesis that in segmentation it is not all the germ-plasm one, it appears to me, can foretell this. My reflections (i.e. idioplasm of the first ontogenetic grade) which is on heredity are not a conclusion, but a commencement transformed into the second grade, but that a midute no complete theory of heredity which claims to provide a portion remains unaltered in one of the daughter-cells, complete solution of all the problems at issue, but re- mingled with its nuclear idioplasm, but in an inactive searches which, if fortunate, may sooner or later, by state ; and that it traverses in this manner a longer or direct or circuitous paths, lead to a true appreciation of shorter series of cells, till, reaching those cells on which the question, to a "real" theory. In the preface to the it stamps the character of germinal cells, it at last assumes English edition of my “Essays” I have stated this i the active state. This hypothesis is not purely gratuitous, expressly.

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but is supported by observations, notably by the remarkI have also in that place distinctly insisted that the able wanderings of the germinal cells of Hydroids frou book was not written as a whole ; that it consists rather their original positions. of a series of researches, the one growing out of the other, But let us neglect the probability of my hypothesis, and and showing the development of my views as they shaped consider merely its logical accuracy: Prof. Vines says :themselves during the course of nearly a decade's work. “The fate of the germ-plasm of the fertilized ovum 13. It is therefore unreasonable to extract ideas from an according to Prof. Weismann, to be converted in part into earlier essay and apply them against a later one. I have the somatoplasm [!] of the embryo, and in part to be left them unaltered, and even “ lest certain errors of inter- stored up in the germ-cells of the embryo. This being pretation uncorrected,” because, if altered, their internal so, how are we to conceive that the germ-plasm of the connection could not have been understood.

ovum can impress upon the somatoplasm [!] of the I believe that the objections which Prof. Vines makes to developing embryo the hereditary character of which it my theory of the continuity of germ-plasma rest solely on (the germ-plasm) is the bearer? This function cannot an unintentional confusion of my ideas, as he compares be discharged by that portion of the germ-plasm of the the opinions expressed in the second essay with those of ovum which has become converted into the somatothe later ones, with which they do not tally. I will en plasm [!] of the embryo for the simple reason that it kina deavour to make this clear. In this second essay (1883) ceased to be germ-plasm, and must therefore have lost the I contrasted the body (soma) with the germ-cells, and ex- properties characteristic of that substance. Neither can plained heredity by the hypothesis of a “Vererbungs- it be discharged by that portion of the germ-plasm of the substanz" in the germ cells (in fact the germ-plasma), ovum which is aggregated in the germ-cells of the embryo, which is transmitted without breach of continuity from for under these circumstances, it is withdrawn from all one generation to the next. I was not then aware that direct relation with the developing somatic cells. The this lay only in the nucleus of the ovum, and could there- question remains without an answer." I believe myself to fore contrast the entire substance of the ovum with the have answered this above. I do not recognize the somato substance of the body.cells, and term the latter "somato plasm of Prof. Vines ; my germ-plasm or idioplasm of the plasm.” In Essay Il'. (1885) I had arrived, like Stras. first ontogenetic grade is not modified into the somato burger and O. Hertwig, at the conviction that the nuclear | plasm of Prof. Vines, but into idioplasm of the second, substance, the chromatin of the nuclear loops, was the ihird, fourth, hundredth, &c., grade, and every one incarrier of heredity, and that the body of the cell was presses its character on the cell containing it. nutritive but not formative. Like the investigators just Prof. Vines also attacks my view of the idioplasmatik named, I transferred the conception of idioplasma, which nature of the nuclear substance (the chromatic grains) : Nägeli had enunciated in essentially different terms, to and maintains that it is as easy to speak of the continuity the “Vererbungs-substanz" of the ovum-nucleus, and of the cell-body as of that of the nuclear substance, and laid down that the nuclear chromatin was the idioplasma that the one may transmit heritable qualities to progen not only of the ovum but of every cell, that it was as well as the other. I quite understand that a botanist the dominant cell-element which impressed its specific may easily be led to this view ; and Prof. Vines is not the

only one to hold it. Waldeyer (" Ueber Karyokinese und universally true ; that Infusoria hindered from conjugahire Beziehung zu den Befruchtungs-vorgänge,". Arch. tion do not die, but increase by division, and may promikr. Anat., xxxii., 1888) has considered the observed duce whole colonies of animals-nay, that they are Escts insufficient to justify the regarding of the nuclear generally thus rendered abnormally prolific. loops as idioplasm ; Whitman (" The Seat of Formative I am distinctly opposed to the rejuvenescence theory, and Regenerative Energy," Boston, 1888) among zoologists whether applied to unicellular or multicellular organisms; basexpressed himself against this view, and the same occurs my view is expressed in Essay IV., and may be sumin the recent book of Geddes and Thomson (“The Evolu- marized in this position-we should no longer speak of tion of Sex," London, 1889). The facts which led me to the conjugating nuclei of the sexual elements as male the idea that the nuclear threads were the real carriers of and female, but as paternal and maternal, there is no heredity-were, in fact, the idioplasma-are enumerated opposition of the one to the other, they are essentially in Essay IV.; they were primarily the observations of E. alike, and differ only so far as one individual differs from van Beneden on the phenomena of fertilization in the another of the same species. Fertilization is no process ovum of Ascaria megalocephala, those of Strasburger on of rejuvenescence, but merely a union of the hereditary fertilization in the Phanerogams by a mere nucleus, and tendencies of two individuals ; tendencies which are the researches of Nussbaum and Gruber on division in bound up with the matter of the nuclear loops ; the cellthe Infosoria. One may further cite as of essential im- body of the ovum and spermatozoon is indifferent in this portance the facts of karyokinesis per se, and the circum- connection, and plays merely the part of a nutritive stance that, only on the supposition that the nucleus matter which is modified and shaped by the dominant contains the idioplasma can the extrusion of polar bodies | idioplasm of the nucleus in a definite way, as clay in the from the animal ovum be rendered comprehensible. The sculptor's hand. The different appearance and function Latter process divides the nuclear substance of the ovum of ovum and spermatozoon, and their mutual attraction, into two quantitatively equal halves, but the body of the rest on secondary adaptations, qualified to ensure that ovum into two unequal halves, the size of which is different they shall meet and that their idioplasmata shall come m every species. The essential part of the process must into contact, &c.; and as with the cells, so the differentiatherefore be the division of the nuclear substance, not tion of persons into male and female is also secondary; that of the cell-mass. These facts on reflection so com- all the numerous differences of form and function which pletely convinced me that the nucleus alone acts as carrier characterize sex in the higher animals, the so-called of hereditary tendencies, that the theory of the physio- “ secondary sexual characters," which reach even into logical equality of the nuclei of the sexual elements which the highest spiritual regions of mankind, are nothing but I had propounded ten years before (1873) struck me as a adaptations to ensure the union of the hereditary tencertainty ; and I then advanced the theory of fertilization dencies of two individuals. wich is contained on p. 246 of Essay IV. I believe These are briefly the views of fertilization which I that till recently Strasburger and I alone had expressed have indicated since 1873, but have only published in a snular views of the essence of fertilization, at least so far finished and definite shape since the discovery by van as relates to the homodynamy of the sexual nuclei. That Beneden of the morphological processes in the fertilizamost distinguished observer, E. van Beneden, who has tion of the ovum of Ascaris (Essay IV., 1885). I conwon such renown in the investigation of the process of cluded then with these words :-"If it were possible to fertilization, took his stand with regard to its theoretical introduce the female pro-nucleus of an egg into another significance on the platform of the older view, which re

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egg of the same species, immediately after the transformagarded it as the union of two elements intrinsically and ' tion of the latter into the female pro-nucleus, it is very essentially the opposite of each other. He could not free probable that the two nuclei would conjugate just as if a himself from that dominant and deeply rooted idea, that fertilizing sperm-nucleus had penetrated (the ovum]. If the difference between the sexes is something fundamental, this were so, the direct proof that egg-nucleus and sperman essential principle of existence. The fertilized oosperm nucleus are identical would be furnished. Unfortunately us in his eyes a hermaphrodite object, uniting in itself the practical difficulties are so great that it is hardly both male and female essences, an idea in which many | possible that the experiment can ever be made ; but such other observers (cf. Kölliker, "Die Bedeutung der want of experimental proof is partially compensated by Zellenkerne für die Vorgänge der Vererbung," Zeit. wiss. the fact, ascertained by Berthold, that in certain Algæ lol., xlii., 1885) have followed him, and of which the (Ectocarpus and Scytosiphon) there is not only a female, logical sequence is that all the cells of the body are to be but also a male parthenogenesis ; for he shows that in regarded as hermaphrodite !

these species the male germ-cells may sometimes develop Van Beneden was also influenced by the idea which into plants, which however are very weakly." sways the naturalists of so many countries, that fertiliza I have since attempted to fertilize one frog's egg with tion is a process of rejuvenescence, in the sense that the nucleus of another; the experiment was, as one without it life cannot be prolonged to the end. Many would expect, not successful, owing to the enormous still hold to this idea ; Maupas ("Recherches expér. sur havoc caused by introducing a cannula into the egg ; but la multiplication des infusoires ciliés,” Arch. zool. exp: , Boveri ("Ein geschlechtlich erzeugter Organismus ohne rén, (2vi. p. 165) very recently believed that he had 'mütterliche Eigenschaften," Ges. Morph. Physiol. Münfound a proof of its correctness, and attempted to show chen, 16 Juli, 1889) was more fortunate, in finding an object that Infusoria, for a continuance of existence, must from which allowed of the converse experiment to mine ; followtine to time enter into conjugation, or die from internal ing Hertwig's example, he removed the nucleus from an causes if this conjugation be prevented. Even were his Echinoid ovum by agitation, and brought such denucleated observations correct, they would still fall short of proving ova to develop by introducing spermatozoa. From the his conclusions: they would prove nothing against the spermatozoan nucleus was formed a regular segmentationimmortality of the Protozoa, or for a rejuvenescence in nucleus, the embryogenesis pursued its regular course, the sense here intended ; they would rather state the and there was formed a complete though small free-swimplatitude that ovum and spermatozoon must die, if the ming larva, which lived for a week. From this experiment condition of their continued existence, namely fusion, alone it follows that the views of Strasburger and myself inevitable in most species of plants and animals, be on fertilization are correct, viz.that the sperm-nucleus can prohutited; but this is an accidental, not a natural, play the part of ovum-nucleus and vice versa, and the death. Richard Hertwig (" Ueber die Conjugation der older view, to which Prof. Vines ("Lectures on the PhysioInfusorien," Munchen, 1889) has also briefly shown that logy of Plants," Cambridge, 1886, pp. 638-681) has also the facts, on which Maupas bases his inference, are not sworn allegiance, must be given up.

An interesting and important modification of Boveri's A further objection is directed by Prof. Vines against experiment confirmed both this experiment, and also, if it my views on the origin of variation. In the fifth essay ! were necessary, the recognition of the nuclear substance have sought the significance of sexual reproduction in the as idioplasm, as maintained by O. Hertwig, Strasburger, fact that it alone could have called into existence that and myself. "If eggs of Echinus microtuberculatus, when multiplicity of form of the higher animals and plants, and artificially deprived of their nuclei, be fertilized with the that constantly fluctuating union of individual variations spermatozoa of Sphærechinus granulatus, larvæ are de of which natural selection stood in need for the creation veloped with the true characters of the second species, of new species. I am still of the opinion that the origin that is to say, they have derived everything from the of sexual reproduction depends on the advantage which father, nothing from the mother; the nuclear substance it affords to the operation of natural selection; nay, 1 an alone it is which transmits heredity, and by it the cell-mass completely convinced that only through its introduction is dominated.

was the higher development of the organic world possible I have interpreted the first polar body of the Metazoan Still, I am at present inclined to believe that Prof. Vines ovum as a carrier of ovogenous plasm, which has to be is correct in questioning whether sexual reproduction is removed from the ovum in order that the germ-plasm the only factor which maintains Metazoa and Metaphyta may attain the predominance. It is possible that this in a state of variability. I could have pointed out in the explanation is not correct; the most recent researches English edition of my “Essays" that my views on this point on the conjugation of Infusoria, as expressed in the had altered since their publication ; my friend Prof. de splendid memoirs of Maupas and R. Hertwig, argue Bary, too early lost to science, had already called my against my interpretation ; but the idea which lay at the attention to those parthenogenetic Fungi which Prof bottom of this explanation is justified. As it is the nu- Vines justly cites against my views, but I desired, on clear matter which gives to the cell-body its specific grounds already mentioned, to undertake no alteration in character, the ovum must, previous to fertilization, be the essays. Bessides, I was well aware when the essay dominated by a different idioplasm to the sperm-cell, was first committed to paper (1886) that my current view since they are, up to this point, different in appearance on the radical cause of variation was possibly incomplete ; and function. On the other hand, when they have and so, in order to expose the truth of the view as far as united, they contain the same idioplasm-namely, germ- possible to a general test, I drove its logical consequences plasmthe consequence is that the first dominant idio- home, and enunciated the statement that species rept plasm is different to that of a later period. This was the ducing parthenogenetically could not be modified into idea at the bottom of my explanation of the first polar new species. I also began myself at that time esperibody, and it is correct. One might perhaps imagine that ments on the variation of parthenogenetic species wiuch the idioplasmata of ovum and spermatozoon were origin- are still being continued, and on which on some fature ally different, but that both possessed the power of occasion I hope to be able to report. alteration into germ-plasm ; but it would be then incom Even if

, however, from our present knowledge it as prehensible why parthenogenetic ova should expel one probable that sexual reproduction is not the sole radica! polar body. Both facts, however, are explicable, if ovum cause of variability of the Metazoa, still no one will dispate and spermatozoon are dominated up to the period of that it is a most active means of heightening variations maturation by different histogenetic idioplasmata with and of mingling them in favourable proportions. I believe which a small quantity of germ-plasm is mingled, and if that the important part which this method of reproducties at a later period the former be removed and the germ- has played in calling out the existing processes of selection, plasm come to rule in both cells. This process

would be is hardly diminished, even if one grants that direct influby no means abnormal and unparalleled, since entirely ences upon the idioplasm call forth a portion of individual analogous divisions of the idioplasm into qualitatively variability. Prof. Vines even holds it probable that dissimilar portions must occur hundreds of times in every the absence of sexuality in these plants [Fungi) FREY embryogenesis

. However, I am most willing to allow be just the reason why no higher forms have been evolved that the last word has not yet been said on this question, from them, for in this respect they present a strikan and would only maintain that my theory of heredity is contrast to the higher Algæ in which sexuality is well not concerned thereby. It is not the interpretation of marked.” But when Prof. Vines says, "there can * the first polar body, but that of the second, which is de- no doubt that sexual reproduction does very materially cisive ; and one can none the less easily think of the latter promote variation," he does not mean to say that this is as a halving of the number of ancestral germ-plasmata, a self-evident proposition ; he is well aware that prouieven if it be proved that my explanation of the first polar nent investigators like Strasburger see in sexual reproduebody was erroneous. I would then express the first tion the reverse action, that of maintaining the constann division merely as introductory to the second, as the of the specific character. But I gladly accept his agres necessary first step in the reduction of ancestral plasmata, ment with my view, which confirms the main position of the necessity for which we should thus perhaps learn to the fifth essay, which runs : Sexual reproduction has understand.

arisen by and for natural selection as the sole means bi The regular modification of idioplasma during the which individual variations can be united and combine ontogeny, which I have maintained and which so many in every possible proportion. have attacked (Kölliker with special vehemence) will With reference also to the problem of the inheritance now stand out as justified. If the nucleus of a sperm-cell of acquired (somatogenic) characters, Prof. Vins 's is capable of impressing on the denucleated mass of an again my opponent; he holds that such inheritance >> ovum its own inherited tendencies, and of calling into possible. I have denied it, because it did not appear to being an organism with specific characteristics purely me self-evident—as was formerly universally assumedpaternal, it will be found difficult to explain the ontogeny but rather utterly unproven ; and because I think that otherwise than as a regular modification of the idioplasm, completely unfounded assumptions of such far-reachmg continuous from one cell-division to another, which stamps consequence should not be made, when requiring a large on the body of each separate cell at each stage its peculiar number of improbable hypotheses for their explication ? character, not only with regard to shape but also to have tested all the available evidence for such inheritance function, and especially with regard to the “rhythm” of as accurately as I could, and have found that none har cell-division.

the value of proof. There is no inheritance of mutilations, 1.“ Das Karyoplasma und die Vererbung : eine Kritik der Weismann'sche and this constitutes up to now the only basis of fact for Theorie von der Continui'ät des Keimplasma's," Zeit. wils. 12001., drive the supposition of the inheritance of somatogenic vanep. 228, 1886.

tions. If, in the last essay, I have not denied every

possibility of such a transmission, Prof. Vines should They were much of the same age, and began their exinterpret that in my favour, not to my discredit ; it is not periments while young at almost the same time ; and the business of an investigator to set forth a proposition, the practical agreement of the conclusions drawn from which on the existing evidence he is compelled to believe, their experimental results is our best guarantee of conas an infallible dogma. Prof. Vines finds my "statements fidence in the modern theory of Thermodynamics which of opinion so fluctuating that it is difficult to determine is built upon these results. wbat (my] position exactly is," but he could have easily Gustave Adolphe Hirn was born at Logelbach, in discovered my meaning, if, instead of promiscuously con- Alsace, on August 21, 1815, and died on January 14 of trasting the eight essays and the eight years of their pro- this year, a victim to the prevailing epidemic of influenza; daction, he had merely brought the last of them to the bar but for this, we might have expected still further developof judgment. This essay is especially concerned with ments of his scientific theories, as he continued at work " the supposed transmission of mutilations," and at its on his favourite subjects to the last. conclusion my verdict on the state of the problem of Self-taught, so far as his scientific education was conthe inheritance of acquired characters is thus summar- cerned, he found himself

, with his elder brother Ferdinand, ised :-" The true decision as to the Lamarckian prin- a manager of the works of Haussman, Jordan, and Co., ciple (lies in) the explanation of the observed phenomena an establishment for the fabrication of indiennes, estabof transformation. . : . If, as I believe, these phenomena lished in 1772. Finding the machinery antiquated and can be explained without the Lamarckian principle, we worn out, Hirn, in setting to work to make the best of it, was have no right to assume a form of transmission of which really better placed for theorizing and experimentalizing we cannot prove the existence. Only if it could be than if he had charge of modern works in first-rate order. shown that we cannot now or ever dispense with the The different parts of the works being at a distance principle, should we be justified in accepting it.” The from each other, his brother Ferdinand brought out his distinguished botanist De Vries has proved that certain system of cable transmission of power ; and it was constituents of the cell-body, e.g. the chromatophores Gustave who pointed out theoretically the advantage of a of Algą, pass directly from the maternal ovum to the thin light cable run at a high speed. daughter-organism, while the male germ-cell generally Hirn also turned his attention to the important economic contains no chromatophores. Here it appears possible question of the lubrication of machinery, and upset the that a transmission of somatogenic variation has oc- previous prejudice against the use of mineral oil for this curred; in these lower plants, the separation between purpose. He also demonstrated experimentally that, while spenatic and reproductive cells is slight, and the body the old laws of friction enunciated by Morin were suffiof the ovum does not require a complete chemical and ciently accurate for the contact of one dry metal against physical alteration to become the body of the somatic another, these laws are powerfully modified when the cell of the daughter. But how does this affect the ques- surfaces are well lubricated, as with machinery. Now the tion whether, for instance, a pianoforte player can trans- friction varies as the square root of the pressure, and as mit to his progeny that strength of his finger-muscles the surface and the velocity; so that the theory falls in which he has acquired by practice? How does this with that of the viscous flow of liquids. These laws have result of practice arrive at the germ.cells? In that lies received confirmation of recent years by the experiments the real problem which those have to solve who maintain carried out under the auspices of the Institution of that somatogenic characters are transmissible.

Mechanical Engineers. It is proved by the observations of Boveri, quoted But it is chiefly for his experiments on a large scale on above, that among animals the body of the ovum con the steam-engines under his charge that Hirn is best tributes nothing to inheritance. If the transmission of known, and from his varied methods of determining the loquired characters should take place, it would have to mechanical equivalent of heat by the friction of metals bye by means of the nuclear matter of the germ-cells--in on metal or water, and finally from observation of the fact, by the germ-plasm, and that not in its patent, but amount of heat consumed by the steam-engine, when 1 irs latent condition.

every source of gain or loss is carefully followed up. To renounce the principle of Lamarck is certainly not With this object he investigated experimentally the ine way to facilitate the explanation of the phenomena ; separate effects of conduction, of jacketing, of initial

I we require, not a mere formal explanation of the condensation in the cylinder, and of its prevention by wrigin of species of the most comfortable nature, but the superheating. real and rightful explanation. We must attempt, there If we watch the performance of a modern marine tripleFore, to elucidate the phenomena without the aid of this expansion engine, we notice that the high-pressure principle, and I believe myself to have made a beginning cylinder appears choked with water from initial condensa

this direction. A short time ago I tried this in one of tion, while the intermediate and low-pressure cylinders hose cases where one would least expect to be able to work comparatively dry. It was considered in the early espense with the principle of modification by use days of compound engines that this initial condensation camely, in the question of artistic endowment.I' I pro- was a source of great loss, and superheating was introposed to myself the question whether the musical sense duced to minimize it. But the superheated steam ruined of mankind could be conceived of as arising without a the packings, and dried up the lubricant, so that the rightening of the original acoustic

faculty by use. But superheater was found practically to do more harm than esea here I came to the conclusion that, not only do we good. A characteristic story is told of John Elder, the sot need this principle, but that use has actually taken pioneer of compounding in modern marine engines, too na part in the development of the musical sense. long to insert here, which bears on this point.

A. WEISMANN. Nowadays this initial condensation is looked upon as

inevitable, and as not really so uneconomical as the THE LIFE AND WORK OF G. A. HIRN.

books make out, when attendant advantages are con

sidered ; but to the theorist such as Hirn this condensaTHE three men who worked at the experimental deter- tion was something to be avoided at any cost, and he

mination of the mechanical equivalent of heat and I worked hard to make its prevention feasible. al practical Thermodynamics have passed away within Hirn was a man of varied reading, taste, and pursuits, a few months of each other-Clausius, Joule, and now and he worked into his treatises on his favourite subject

Gedanken über Musik bei Thieren und bei Menschen, Deutsche physics, which make his books rather curious reading anda dax, October 18Bg.

sometimes to modern tastes, and we must go back to the

.

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