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Some verbal inaccuracies which had crept into the first Bibliothèque photographique : Le Cylindrographe, Ap translation have been corrected, and in every respect the pareil panoramique, Par P. Moossard, Commandant editor may be congratulated on the work in its present du Génie breveté, attaché au Service géographique de form. It will be of the greatest use to students-espe l'Armée. (Paris : Gauthier-Villars, 1889.) cially, perhaps, to those who have to work alone.

This is a description of a photographic camera invented D, H. S.

by Colonel Moëssard, in which the lens is pivoted on an

axis, and the sensitive film is arranged in a cylindrical Traité d'Optique. Par M. E. Mascart. Tome I. (Paris: form about this axis, on a radius equal to the focal length Gauthier-Villars, 1889.)

of the lens. By this means a panoramic view of angula

breadth up to 170° can be taken. The camera being fixed This is the first half of a very elaborate treatise on in position, the lens is uncapped, and then rotated quickly optics, the full scope of which we cannot tell till the or slowly, according to the speed of the plate, and the er second volume appears, as no hint is given of what is tensity of light in any direction. The author claims fre yet to come. This first volume begins with the funda- the instrument useful employment in surveying, erther mental principles of the wave-theory of light, deduces the carefully detailed plans of an ordnance survey, or 10 from them the elementary laws of geometrical optics, the rapid views useful for warlike purposes, which their discusses the properties of a co-axal system of refracting strument can afford. Two photographs taken with the 2: surfaces, describes the structure of the eye, expounds the of the instrument illustrate very favourably its powers. facts of colour-mixture, points out the conditions which especially for architectural purposes. determine the resolving power of a telescope, develops at great length the theories of diffraction and interference, A Hand-book of Modern Explosives. By M. Eissie: with some of their principal applications, and devotes (London : Crosby Lockwood and Son, 1889.) about 80 pages to polarization and double refraction. There is practically nothing about the microscope, and In this book the author of “ Modern High Explosives" nothing at all about the paths of rays in media of con- has collected much useful information about the various tinuously varying density.

explosives now in use. The greater part of the work is The book is by no means easy reading, and the labour devoted to nitro-compounds, but short accounts of the of perusing it is increased by the smallness of the refer- other types of explosives now being manufactured are ence letters (with their numerous accents and suffixes)

added. The manufactures of gun-cotton and nitrowhich occur in the figures. The plan involves much glycerine receive full treatment, together with the modis specialization. For instance, the proof of the formula for cations introduced in the various large factories both oo retardation on which the theory of Newton's rings de America and Europe. The important subject of the use pends is not given in the sections devoted to Newton's of explosives in fiery mines has a chapter to itself. The rings and colours of thin plates, but some 370 pages especial interest ; in fact, the official reports of the ress

description of the tests of flameless powders is at earlier. In many cases, when the student has found a of many of the most important explosives are perhaps formula which appears to contain the information of which he is in quest, he has to search carefully through the most instructive portions of the book. The chape a long series of preceding pages before he can find the dealing with the practical application of explosives show meaning of some symbol which occurs in it. The volume be useful not only to the miner, but also to officers contains a vast store of information, but not generally in /

both services to whom blasting and the use of explosive a form to suit hasty seekers after truth. It requires to Än interesting account of the history and trials of he

generally may at any time become a necessary auxilar be studied at leisure, and the time so spent will not be Lalinsky gun, together with the manufacture and use it wasted. Great pains have obviously been taken to embody the latest information and present it in the clearest gun-cotton shells, is also well worthy of their perusai form. We may instance the spiral curves which illustrate Little is said on the use of explosives belowwale the values of Fresnel's integrals, and the curve (to which especially on the subject of the removal of wrecks, while' a folding-plate is devoted) showing the relations of would stand far fuller treatment. Four appendices ar the colours of diffraction fringes to the three primary added, two dealing with the analysis and determinataan colours. There is an excellent discussion of the theory from the principal provisions

of the Explosive Act of 18-3 of concave gratings, both for reflection and refraction. The least attractive chapter is that entitled “ Properties Although there is much that is necessarily old, still the :: of Vibrations.” It is a discussion of the composition of a book that will be read with interest by most who in simple harmonic motions, and occupies 40 pages bristling tions are well executed, and the whole wonderfully free

The illustra with elaborate formulæ. We think a more moderate display of mathematics under this head would have

from printer's errors. sufficed.

The order of arrangement adopted in the volume is rather peculiar, and baffles all a priori conjecture. For

LETTERS TO THE EDITOR. instance, the discussion on colour-mixtures occurs in a chapter on “Interferences," and the investigation of the (The Editor does not hold himself responsible for opinions conditions which determine the resolving power of a

pressed by his correspondents. Neither can he undertak telescope is given in the introductory chapter under the

to return, or to correspond with the writers af, atra head of “Preliminaries.”

manuscripts intended for this or any other part of Natuu

No notice is taken of anonymous communications. ] The book is essentially a mathematical treatise, all experimental descriptions being reduced to the narrowest The Peltier Effect, and Contact E.M.F. possible limits.

Without any further reference to the heading of a letter v The preface states that the work is addressed mainly p. 102, signed The Reviewer," I wish to discuss an interestia to "pupils of the Faculties and Schools of higher in argument therein propounded as proving that a true elecstruction," but we think its principal use in this

country motive force at contact between two metals cannot lie the one will be as a book of reference for teachers. Its value for, or sole cause of the Peltier efiect, unless the latter le 31m) this purpose will be greatly increased if a good alpha- proportional to absolute temperature. The arguinert is van betical index is added at the end of the second volume. like one that I indistinctly remember to have heard suggese

some time ago by Prof. Schuster, and it struck me at the tire J. D. EVERETT. as ingenious and not easily answerable.

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On seeing it in print, however, a natural answer occurs to me, It was a fine cool day and quite calm. In the afternoon a false which it may be worth while to give. The whole point of the or mirage horizon about 3° above the true one was visible for a reasuming depends on assumed properties of vacuum.

few hours. No objects were within range of vision. The The assumptions are as follow:

mirage disappeared as the sun declined. {") That a perfect vacuum is an absolute non-conductor of The next day was very much warmer, and we saw a more electricity.

marked and interesting mirage in the afternoon as we were (2) That no contact E M.F, exists between a metal and a steaming across the Sea of Marmora away from Constantinople. vacuum.

In this case it appeared only in the west, and objects were seen 13) That vacuum has a specific inductive capacity.

reflected in an inyerted position. A small conical-shaped island Grant all these, and the argument is sound. Decline to was seen with its inverted image at times distinct from and at atimit any of them, and it proves nothing. Break down the times blending with the original. The image was distinctly furst two of them, and it proves too much: it proves the non- seen of some land, which was actually below the horizon. The exrstence of any thermal contact-force whatever between con mirage of the reflection of the sun in the sea was, when seen ductors

. For if there were any E.M.F. at the metallic contact, through a glass, especially beautiful. It resembled a glorious and note at the other or vacuum contacts, a continuous current cataract of golden water. This mirage lasted till quite the dusk would flow, propelled by energy derived from a cold place. of the evening, and then gradually thinned down and died

This argument is indeed the ordinary one to prove that the away. algebraic sum of the E.M.F.'s at all the junctions of a closed I do not know whether mirages at sea are uncommon; but as ciucting circuit in which no energy but heat is supplied must the officers on board did not remember seeing one before, I loc pero when the temperature is uniform.

thought these instances might be worth recording. The prauf scarcely holds when insulators are interposed,

ARTHUR E. BROWN. thusogh the fact may be true nevertheless. When chemically Thought Cot, Brentwood, December 31, 1889. zecive slistances with their extraneous supply of energy are mlerposed, the fact itself is no longer true. But how do we know what is true when vacuum is interposed? The hypothesis

Self-luminous Clouds. ra wuch the argument is founded is a baseless conjecture. I am very sorry that I took no notes, some six or seven years

That it may be said, Are not the hypotheses probable? Do ago, on the first and only occasion of my seeing self-luminous fwa not yourself believe them? I believe in (1) and (3) pro clouds, but though I can give neither date nor positions, the woonally, but certainly not in (2). The contact E.M.F. be following facts are still fresh in my memory. {ween twu substances is probably some surface action or skin Passing through Bushey Park after dark, I noticed an aurora phenomenon, and I see no reason why it should not occur as borealis, and, as I had only recently seen the rather rare well in the boundary between metal and void as in the boundary phenomena of the rays of the setting sun converging towards a letween one metal and another. Indeed, it is not improbable point in the east, I followed the direction of one of the principal that the same of the E.. M.F.'s in every circuit of chemically inert beams of light towards the south, when, at a point somewhat ubstances, whether conducting or not, and inclusive of vacuum, south of my zenith, I noticed an equatorial belt of luminous 15 Pro under uniform temperature conditions.

clouds. I found that each cloud belonged to a ray, and faded All thar la wanted to establish this is the knowledge that in a and brightened with it, but was separated by about 60° of clear surant of any one substance at non-uniform temperature the sky. This belt of clouds extended down to the western horizon, al E M.F. shall be zero,' or that the Thomson effects in a the eastern one was obstructed by trees, while shortly afterwards ingle substance always balance each other ; 1.1. that the total small dark clouds appeared on that side, and the sky soon L.M.F. in a circuit shall depend on a potential function of became overcast. temperalure, or dE = f()dt.

The luminous clouds were quite transparent, so that even Now it is quite true that this f"(?) is the Peltier coefficient faint stars could be seen through them when at their brightest. unded by absolute temperature, and that st) in its most general I have heard from Scandinavian captains that these luminous form contains an arbitrary constant, but what of that? Nothing belts are sometimes seen in northern latitudes, and are sure signs known of (*) except that it is a potential function : it is not of bad weather. I have written these few remarks in the hope known to represent any physical effect. I never said that the that those of your readers who may have the chance of seeing Peltier effect enabled us to find the most general form of the an aurora borealis will also look out for these clouds, and if function fio); I said it gave us the E.M. F. at a junction. possible determine their position.

C. E. STROMEYER. And there is much ground for the assertion ; for it is easy to Strawberry Hill, January 4. zbow that in a simple AB circuit, with junctions at , and ty, the total E.M.F. is

The Revised Terminology in Cryptogamic Botany. E = 11 - 11, + OA - )dt;

The anglicized forms of most of the terms in common use,

employed in the "Hand-book of Cryptogamic Botany." recently fut as if the resultant E.M.F. were the algebraic sum of two issued by Mr. G. Murray and myself

, have not up to the present Pellier E.M.F.'s and of two Thomson E.M F.'s.

time found much support from our fellow-botanists. I propose, My only contention is that this equation, which is undeniably therefore, to give, in some detail, the reasons which have true when the 11 are interpreted as heat-coefficients, is also true induced us to adopt them, and to urge their general use on writers and immediately interpretable when they stand for contact on cryptogamic botany. For this purpose we will take as our text EM.E.The burden of proof as to the physical existence of an

extracts from three reviews of the “ Hand-book," marked, as all unhecessary and in every sense arbitrary constant rests with

the critiques have been, with only one or two exceptions, by a the who doubt this simple explanation.

generous appreciation of the difficulties of our task, and a too Ir is difficult to See how a doubt can arise, or how the Peltier great leniency to the many shortcomings of the work :-“ The smut Thomson productions or destructions of heat can be ac

most conspicuous, though not the most important, of these sunted for without local E. M.F.'s. Nobow, so Dr. Hopkinson (changes) is the adoption of anglicized terminations for Latin u proved, and I also have insisted (Phil. Mag., October 1885, and Greek technical words. This is a matter in which it is and March 1886), except by some wildly gratuitous assumption hard to draw the line aright

. . . . As a matter of taste we vil an actual physical specific heat for electricity, dependent on the

think the authors have gone much too far in this direction. Temperature and on the metal in which it happens to be.

They complain of the 'awkwardness and uncouth form of these Liverpool, December 14, 1889. OLIVER J. Lunge.

words '; we should have thought the reproach applied much more strongly to 'cænobe,' sclerote,' 'nemathece,' and

columel'" (NATURE). "An Englishman may guess what Mirages.

archegone' is short for, for example ; but why puzzle a Tue anide in NATURE of November 21, 1889 (p. 69), recalls in every treatise hitherto written on the special subject in any

foreigner with a new form of a word with which he is familiar 1. me mirages I saw in March 1888, while travelling in the European language?” (Academy). "Too sanguine expectations Laul on the steam yacht Ceylon. On the 29th we were crossing the Black Sea from Sebastopol. complete failure of the somewhat similar experiment made by

on this head might well be toned down by remembering the * Hopkinson virtually printed this cur, Phil. Mag., October 1885. Lindley. . . .Primworts, spurgeworts, bean-capers, and hip

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purids are decidedly simpler, even if less euphonious, than Primu. Italian ; but still that of the highest authorities is, on the whole faceæ, Euphorbiaceæ, Zygophyllace, and Halorageæ ; yet the very decidedly in favour of French, rather than Latin or Greek, longer Latin terms are still universally used, while the quasi forms of the words in most common use. From works picked English ones have never obtained even temporary acceptance" up almost at random, we select the following :(Journal of Botany).

The last of these criticisms appears to rest on a confusion Anthéridie Van Tieghem, Parenchyme Guignard, Hecbetween the principles of nomenclature and those of terminology. Guignard, Philibert, De kel, Fayod, Bonnet In nomenclature, rigid rules have been laid down, and accepted Wildeman, Bornet, Thuret. Tulasne. by all leading naturalists of all countries, in order that the Archégone Van Tieghem. Perithire Costantin. scientific names of species, genera, orders, &c., may correspond in Baside Tulasne, Rou. Pollinide (Floridex) Guignard. scientific treatises in all languages. In the terminology of meguère (basidie, Fayod). Prorarpe Bornet, Thuret. flowering plants no such rule has ever been attempted to be laid Capitule Bornet.

Propagule Bornet. down; but each writer, when writing in his own language, uses Conilie Costantin, Rou.

Guignard terms, usually of classical origin, and derived from common roots, meguère (conid, Bornet). Premi

Costantin, Roubut of a form as far as possible amenable to the laws of the Epiderme Van Tieghem, meguère. language in which he writes. All that we are contending for is

Renault,

Sclerote Van Tieghem the extension of the same principle to cryptogamic botany; one Favelle Bornet, Thuret.

Fayod. of the main objects in the publication of our " Hand-book "being Gamétange De Wildeman, Sore

Thuret to make the study of flowerless plants as attractive to the public Glomérule Bornet, Tulasne. Sporange Bornet, Tharet, at large as is that of flowering plants,

| Gonidie De Wildeman. Roumeguere, Tulazne, Van In order to show how recent is the universal adoption of this Hormogonie Bornet.

Tieghem, De Wildeman, practice in phanerogamic botany--a change largely due to the Hyphe De Wildeman. Guignard, Philibert. influence of Dr. Lindley's writings-we append à list of a few Nucléole Guignard. Stipe Fayod, Roume terms in use in standard works of original research or of reference, Oogone De Wildeman guere. published within the last thirty-two years, which presented (oogonie, Roumeguère). Stomate Philibert, The themselves the first to our hand ; viz.-" The Miscellaneous Opercule Philibert.

ret. Botanical Works of Robert Brown” (1866); Mr. Currey's Ostiole

Thuret, De Thalle Tharet, Gay, translation of "Hofmeister on the Higher Cryptogamia, &c."

Wildeman.

De Wildeman, Fayod. (1872); Berkeley's "Introduction to Cryptogamic Botany' Paraphyse De Wildeman. i Zoosporange Flahaul. (1857); and Bentley's “Manual of Botany" (2nd ed., 1870) =

The great stronghold of the conservatives in terminology is Achanium Bentley Ovulum

Brown the German language. No doubt a large mumber of the best Anthera Brown

Perianthium Brown writers do here maintain the classical form of most technica? Arillus Bentley Pericarpium Brown cryptogamic terms, including some in which it has already been Bractea Brown

Pistillum Brown abandoned with us, such as conceptaculum, rereptacular, Carpellum Brown

Rhizoma Berkeley stolo, and perianthium, just as we still meet with anus Integumentum Berkeley Spermatozoon Currey ovulum, and protoplasma. This is no doubt largely due to the Involucrum Brown Stamina (plural) Brown greater difficulty which the German language has than the Ovarium Brown

Stipula Currey French or our own in naturalizing aliens. But even here the With the exception of words which have been incorporated coming yearly more and more into use. In order that there may

practice is by no means uniform, and Germanized forms are into our language, such as corolla, nucleus, &c., few of those used in describing flowering plants now retain their be no question as to the recency and authority of the examples classical forms; the most conspicuous exceptions being those standard treatises in Schenk's "Handbuch der Botanik"; her!

quoted, the following list has been compiled exclusively from the applied to the structure of tissues, such as epidermis and those other works of equal authority been consulted, the list might ending in enchyma ; and can anything be more puzzling than have been considerably extended :the forms in common use for the terms derived from the Greek dépua-epidermis, hypoderma, and periderm? We have no Apophyse Goebel

| Hormogon Zopf doubt that, had our critic lived in the days of Robert Brown Archespor Goebel

Mycel Zimmermann and Lindley, he would have thought all the innovations intro Basidie Zopf

Paraphyse Zopf duced by the latter “uncouth" simply because we were not Carpogon Falkenberg Parenchym Haberlandt, Zimused to them; and would have said that Lindley had “gone Cilie Zopf

mermann, Detmer, Schenk, much too far." In some of those adopted by ourselves we have, Collenchym Haberlandt, Zim. Zopf in fact, been forestalled by others, as in the cases of antherid and mermann

Plasmod Zopf archegone by Lindley, and sporange by Oliver.

Conidie Zopf

Prokarp Falkenberg We now come to the charge made by our critic in the Endospor Goebel

Sklerenchym Haberlandi, DetAcademy, that the terms we have introduced would Enzyme Zopf

mer, Schenk ** puzzle foreigners.” Unfortunately, our polyglottism, or rather Epithel Haberlandt Sporogon Goebel oligoglottism, will not allow us to vie with our reviewer in his | Exospor Goebel acquaintance with every European language ; we are compelled to confine ourselves chiefly to three; but these include by far We do not mean that these words are exclusively used by the the greater part of European botanical literature-in fact, every writers quoted; it is not uncommon to find the Latin and the treatise which nine out of ten English readers will wish to con. German form used indifferently on the same page. It is note sult in the original. The statement quoted above seems to have worthy also that even the most rigid conservatives do not use the been rashly made.

Latin form in the plural of such words as "oogonium," "sporanIn Italian, as far as our knowledge goes, the practice is gium,""* antheridium," "sclerotium,"&c., but always the German absolutely uniform: no botanical writer of repute uses the forms, Oogonien, Sporangien, Antheridien, Sklerotion, &c. : such classical forms ; but every technical term has its Italian spelling words as "oogonia," "sporangia," "antheridia," " sclerotin, and termination. To such an extent is this adaptation to the &c., are, as far as our experience goes, to be found only in laws of orthography of the language carried, that we find English and American writings and in Latin diagnoses. "xylem " converted into xilema, "phloem”in to floema, Analyzing, therefore, the statement that the Latin and Greek " hormogonium ”into ormogonio, and " hyphæ” into ifé ; and forms of words used in cryptogamic terminology are "fatiliar this by the first writers "on special subjects."

in every treatise hitherto written on the special subject in any Our acquaintance with Swedish, Danish, Dutch, and Spanish European language," we find that in Italian the practice is is too slight to allow us to speak with confidence ; but in all unanimously, and in French (as also, we believe, in most other these the general practice is, we believe, the same as in Italian, European languages) preponderatingly in the opposite direction. though not to the same extent; with the best writers, when and that German is the only widely read language of Continental writing in their own language, the use of terms with Latin or Europe in which even the weight of authority is still on that Greek terminations appears to be the exception rather than the side. rule.

There are some terms in which, no doubt, the classical for In French, the practice is by no means so uniform as in must be retained, especially those which, when deprived of ther

classical termination, become monosyllabic, such as "thallus," Weismann's recent essays, is of a very different order - soras," , "bypha," and "ascus," just as we still speak of a from that forming the main position of the so-called ** corolla," a "stigma," : "hilum," and a ** raphe." But, with Neo-Lamarckians in America. It is true that most regard to the great majority of terms in current use in descriptive American zoologists, somewhat upon Semper's lines, yptogamic botany, we entertain not the smallest doubt that the have supported the theory of the direct action of environforzy years, become established in phanerogamic botany, and we ment, always assuming, however, the question of transwould venture to suggest to our fellow-workers in cryptogamic mission. But Cope, the able if somewhat extreme betany in this country and in America, whether it will not be advocate

of these views, with Hyatt, Ryder, Brooks, Dall, is to accept it frankly once for all.

and others, holding that the survival of the fittest is now ALFRED W. BENNETT. amply demonstrated, submit that, in our present need of

an explanation of the origin of the fittest, the principle of selection is inadequate,

and have brought forward and Exact Thermometry.

discussed the evidence for the inherited modifications

' produced by reactions in the organism itself-in other I Ax quite ir agreement with Prof. Sydney Young (NATURE, words, the indirect action of environment. The supposed December 19, p. 152), that after the lapse of a sufficient time , arguments from pathology and mutilations have not been let us say. sa infinite time-the constant slow rise of the zero considered at all: these would involve the immediate point of a thermometer at the ordinary temperature will attain a inheritance of characters impressed upon the organism and lieating the thermometer to a high temperature is simply to not springing from internal reactions, and thus differ both increase the rate at which this final state is approached. If the in the element of time and in their essential principle from results of experiment at the ordinary temperature be expressed the above. As the selection principle is allowed all that in a mathematical formula which admits of making the time Darwin claimed for it in his later writings, this school infinite, the limiting value of the rise on that condition) will stands for Lamarckism plus-not versus-Darwinism, as pot exceed on the average 2° C., even in a thermometer of lead Lankester has recently put it. There is naturally a lase After exposure to a high temperature, and in the same diversity of opinion as to how far each of these principles tbermometer, so great an ascent as 18° C. is a possible measure- is operative, not that they conflict. ment, actually realized. The two phenomena are therefore very The following views are adopted from those held by differcat in their nature.

Cope and others, so far as they conform to my own The view that, owing to the more rapid cooling of the outer observations and apply to the class of variations which parts of the bulb after it has been blown, the inner parts are in a come within the range of palæontological evidence. In state of Sension, and that it is the gradual equalization of the ersion throughout the glass that causes the contraction, has the life of the individual, adaptation is increased by local frequently been held, and

will probably be for a long time the and general metatrophic changes, of necessity correlated, invourite bypothesis upon the subject. It breaks down, however, which take place most rapidly in the regions of least when we attempt to calculate what the amount of the contraction perfect adaptation, since here the reactions are greatest; migte be, on the supposition that it is well founded : only a very the main trend of variation is determined by the slow

all portion of the contraction could be thus accounted for transmission, not of the full increase of adaptation, but of i regret that I caminot now conveniently refer to Guillaume's the disposition to adaptive atrophy or hypertrophy at interesting demonstration of this result.

I certain points; the variations thus transmitted are Prof. Young has placed on record an experiment with three / accumulated by the selection of the individuals in which hermometers, which be heated to 280°C. The zero movement, they are most marked and by the extinction of inadaptive however, moly ranged from 1° to 1° 3, --small readings which varieties or species: selection is thus of the ensemble of hermometers at other times. It is consequently very difficult to new and modified characters. Finally, there is sufficient draw any inference from this experiment. I may, however, palæontological and morphological evidence that acquired mention that closed thermometers

made of lead glass are very characters, in the above limited sense, are transmitted. am bo show a rise of zero after heating to about 120° C. and In the present state of discussion, everything turns Ipwards to sume temperature in the neighbourhood of 270° C., , upon the last proposition. While we freely admit that and after that a descent of zero; the temperature of 280° C. transmission has been generally assumed, a mass of Kould m that case be an unsatisfactory one for a test experiment, direct evidence for this assumption has nevertheless od the effect of plasticity might very possibly be masked. On been accumulating, chiefly in the field of palæontology. the other hani, if the three thermometers were of hard glass, all This has evidently not reached Prof. Weismann, for be zero movements would in that case be greatly diminished, no one could show a fairer controversial spirit, when and the results would be in less bold relief. I do not know any substance more curious or interesting in its forward can be accepted as proof of the assumption.” It

he states repeatedly: “Not a single fact hitherto brought properties than glass; and I should be glad if Prof. Young.. is, of course, possible for a number of writers to fall lett my suggestion that plasticity is the main cause of the zero together into a false line of reasoning from certain facts; ascent after 120*C. Probably it has little or nothing to do with it must, however, be pointed out that we are now deciding tise ascent at the ordinary temperature. It is, however, known between two alternatives only, viz. pure selection, and thas fine threads of glass are undoubtedly plastic at the ordinary selection plus transmission. temperalore.

EDMUND J. Mills. The distinctive feature of our rich palæontological eviMelros, X.B., December 29, 1889.

| dence is that it covers the entire pedigree of variations:

we are present not only at but before birth, so to speak. Among many examples, I shall select here only a single

illustration from the mammalian series-the evolution of THE PALÆONTOLOGICAL EVIDENCE FOR the molar teeth associated with the peculiar evolution of

THE TRANSMISSION OF ACQUIRED the feet in the horses. The feet, starting with plantigrade CHARACTERS.

bear-like forms, present a continous series of readjustments

of the twenty-six original elements to digitigradism which and Germany in support of the transmission of selectionists would explain this complex development and acquired characters, which has been so ably criticized in reduction by panmixia and the selection of favourable

fortuitous correlations of elements already present, the 'This article is an informal reply to the position taken by Prof. Weismann teeth render us more direct service in this discussion, since na mas saya upas heredity. I have borrowed freely from the materials of they furnish not only the most intricate correlations and 1. pred Brea, al others, without thinking it necessary to give acknowledg- readjustments, but the complete history of the addition De in each cara

of a number of entirely new elements-the rise of useful skeleton, all coincident with those in the teeth ; (d) finaliy. structures from their minute embryonic, apparently useless, all the above new variations, correlations and readjusicondition, the most vulnerable point in the pure selection ments, not found in the hereditary germ-plasm of one theory. Here are opportunities we have never enjoyed period, but arising fortuitously by the union of different before in the study of the variation problem.

strains, observed to occur simultaneously, and to be The first undoubted ancestor of the horse is Hyraco- ' selected at the same rate in the species of the Rocky therium; let us look back into the early history of its multi- Mountains, the Thames Valley, and Switzerland! These cuspid upper molars, every step of which is now known. assumptions, if anything, are understated. Any one of Upon the probability that mammalian teeth were developed 'them seems to introduce the element of the inconstant, from the reptilian type, Cope predicted in 1871 that the whereas in the marvellous parallelism, even to minute tech first accessory cusps would be found on the anterior and markings and osteological characters, in all the widely disposterior slopes of a single cone, i.e. at the points of tributed forms between Hyracotherium and Equus, the interference of an isognathous series in closing the jaws. most striking feature is the constant. Viewed as a Much later I showed that precisely this condition is filled whole, this evolution is one of uniform and uninterrupted in the unique molars of the Upper Triassic Dromotherium. progression, taking place simultaneously in all the details These with the main cusp form the three elements of the of structure over great areas. So nearly does race adapitritubercular crown. Passing by several well-known ation seem to conform to the laws of progressive adaptation stages, we reach one in which the heel of the lower molars in the individual, that, endowing the teeth with the power intersects, and, by wearing, produces depressions in the of immediate reactive growth like that of the skeleton, we transverse ridges of the upper molars. At these points can conceive the transformation of a single individual are developed the intermediate tubercles which play so from the Eocene five-toed bunodont into the modern important à rôle in the history of the Ungulate molars. horse. So, without a doubt, every one of the five main component The special application of the Lamarckian theory fa cusps superadded to the original cones, is first prophesied the evolution of the teeth is not without its difficulties

, by a point of extreme wear, replaced by a minute tubercle, some of which have been pointed out to me by Mr. E. 5. and grows into a cusp. The most worn teeth, i.e. the first Poulton. To the objection that the teeth are formed true molars, are those in which these processes take place before piercing the gum, and the wear produces a loss ei most rapidly. We compare hundreds of specimens of tissue, it may be replied that it is not the growth, but related species ; everywhere we find the same variations the reaction which produces it, which is supposed to be at the same stages, differing only in size, never in position. transmitted. Again, this is said to prove too much ; why We extend the comparison to a widely separate phylum, is the growth of these cusps not continuous ? This may and find the same pattern in a similar process of evolution. be met in several ways : first, in the organism itself Excepting in two or three side lines the teeth of all the these reactions are least in the best adapted structures, s Mammalia have passed through closely parallel early proposition which is more readily demonstrated in the stages of evolution, enabling us to formulate a law : The feet than in the teeth-moreover, since the resulting new main elements of the crown make their appearance at growth never exceeds the uses of the individual, there is the first points of contact and chief points of wear of the a natural limit to its transmission ; secondly, the growtha teeth in preceding periods. Whatever may be true of of the molars is limited by the nutritive supply-we spontaneous variations in other parts of the organism, these observe one tooth or part growing at the expense of new cusps arise in the perfectly definite lines of growth another ; third, in some phyla we do observe growth Now, upon the hypothesis that the modifications induced which appears to lead to inadaptation and is followed to in the organism by use and disuse have no directiveinfluence extinction. In one instance we observe the recession w upon variations, all these instances of sequence must be one cusp taking place pari passu with the development of considered coincidences. If there is no causal relation- the one opposed to it. These and many more genera! ship, what other meaning can this sequence have? Even if objections may be removed later, but they are of such useful new adjustments of elements already existing may force that, even granting our own premises, we cannor arise independently of use, why should the origin of new now claim to offer a perfectly satisfactory explanation elements conform to this law? Granting the possibility all the facts. that the struggle for existence is so intense that a minute The evidence in this field for, is still much stronger than new cusp will be selected if it happens to arise at the that against, this theory. To sum up, the new variationright point, where are the non-selected new elements, the in the skeleton and teeth of the fossil series are observed experimental failures of Nature? We do not find them to have a definite direction ; in seeking an explanation of Palæontology has, indeed, nothing to say upon individual this direction, we observe that it universally conforms to selection, but chapters upon unsuccessful species and the reactions produced in the individual by the laws of genera. Here is a practical confirmation of many of the growth ; we infer that these reactions are transmitted !! most forcible theoretical objections which have been the individual is the mere pendent of a chain (Galton urged against the selection theory.

or upshoot from the continuous root of ancestral plasma Now, after observing these principles operating in the (Weismann), we are left at present with no explanation teeth, look at the question enlarged by the evolution of of this well-observed definite direction. But how cao parallel species of the horse series in America and Europe, this transmission take place? If, from the evideat and add to the development of the teeth what is observed necessity of a working theory of heredity, the mwi in progress in the feet." Here is the problem of correlation probandi falls upon the Lamarckian-if it be demonstraten in a stronger form even than that presented by Spencer that this transmission does not take place--then we are and Romanes. To vary the mode of statement, what driven to the necessity of postulating some as yer unmust be assumed in the strict application of the selection known factor in evolution to explain these purposive ai theory? (a) that variations in the lower molars correlated directive laws in variation, for, in this field at least, the with coincident variations of reversed patterns in the old view of the random introduction and selection of De® upper molars, these with metamorphoses in the premolars characters must be abandoned, not only upon theoretical and pocketing of the incisor enamel ; (6) all new elements grounds, but upon actual observation. and forms at first so minute as to be barely visible Reading between the lines of Weismann's deeply immediately selected and accumulated ; (c) in the same interesting essays, it is evident that he himself is coming individuals favourable variations in the proportions of the to this conclusion HENRY FAIRFIELD OSHORX. digits involving readjustments in the entire limbs and Princeton College, August 23.

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