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is also seen in the attempt to combine a more general | hydra in preparations simply traced up in water and treatment of the subject with practical directions.

stained with methyl-blue, and in optical sections of the General instructions with regard to the microscope, entire animal prepared with osmic acid. We may microtome, and reagents, are given in the introduction ; mention that it has recently been shown by Albert Lang these, however, do not indicate a very wide personal that the bud in hydra is not “a product of both acquaintance with the ordinary laboratory requirements, ectoderm and endoderm” as stated on p. 223. The and the methods of preparation, &c., are mainly copied Metazoa are said to be all “characterized by ... the from Lloyd Morgan's “ Animal Biology” and Howes's possession of a digestive cavity (enteron)” (p. 224). On ** Atlas of Practical Elementary Biology.” The student p. 234 we read that the "kidneys (nephridia)" of the is referred to a number of well-known text-books for mussel are "sacculated organs whose walls carry a mass further information, but it is curious that no mention is of tubules," and one gathers that the small irregular made of certain excellent elementary works treating more opening leading from the kidneys into the “ureter” is especially of the types described.

quite easy to recognise. Fig. 194A, representing the brain The part dealing with plants, which occupies rather of the frog, is taken from the old figure by Ecker, in more than half the book, is on the whole more satis which the "olfactory lobes” are separated by a cleft, and factory and contains fewer mistakes than that relating to the primary fore-brain is said to be the same thing as animals. Most of the woodcuts in the former are taken the thalamencephalon (p. 333). We do not see the object from well-known sources, and a number of original of introducing a description of the complicated human figures are given of Aspidium and of Lamium album, auditory apparatus in the chapter on the frog. The which latter is selected as a type of the Phanerogams; account of the processes of maturation, fertilization, and the author has evidently worked out the structure of these segmentation of the ovum of the frog is extremely incomforms with some care. In the zoological part many of plete and inaccurate, and one might even infer from Lloyd Morgan's diagrams have been utilised, and figures one sentence on p. 331 that the nucleus was quiescent are also taken from various other text-books, such as during the division of the egg ! We are told that the Milnes Marshall's “ Frog," Wiedersheim's “Comparative ectodermic invaginations which give rise to the “nares” Anatomy," and Quain's " Anatomy." Most of those from become “continuous with the mesenteron” (p. 335). the last-named work, with the corresponding descriptions, The description of the development of the lungs (p. 334), naturally do not refer to the frog at all, but this fact is not together with the figure copied from Wiedersheim, stated. Some of the drawings of invertebrates made by refer to the inam mal, and not to the frog. In the author are very fair, though they do not indicate much the account of the development of the bodyoriginality; one or two others, such as that of an undis cavity (p. 335), it is said that the latter, “ extended charged nematocyst of hydra, on p. 221, are bad. The upwards through the lateral mesoblastic plates, nearly sources from which borrowed figures are taken is not meets in the middle line beneath the notochord, and so mentioned in all cases, although the contrary is stated in pinches the alimentary canal with its glands into the the preface.

body cavity”; and on page 333 it is stated that the The author shows very little power of selecting his facts, notochord “pierces the mesoblast and divides it into or of drawing conclusions from them in such a way as to right and left halves." The numbering of the five clearly illustrate the general principles of the subject. aortic arches given in Fig. 225, and that of the three Many of the details, moreover, are incorrect, and errors mentioned in the text is incorrect (p. 336). We learn of the most serious character occur. It will be sufficient | that metamorphosis begins soon after the developto refer to a few of these in order to indicate the author's ment of the gills (p. 336). The account of the looseness of expression and want of acquaintance of parts development of the urinogenital ducts on p. 338 is of the subject with which he deals.

quite incorrect as applied to the frog. In Chapter The remarks on the structure and functions of the XVIII. one gathers that the processes of digestion nucleus, and on the pulsating vacuole in protococcus in all the Colomata are quite similar to those which (pp. 46 and 47) are, to say the least, misleading. This occur in the higher forms, which are then briefly deorganism may, it is said, " be looked upon as a closed bag scribed. with a double wall-the outer of cellulose, and the inner Even if we accept the author's dictum that “he will of protoplasm” (p. 50), and the movements of its cilia know a good deal of botany who knows Chara and Lamium “probably" drive it through the water (p. 48). The in- thoroughly," and give him full credit for having worked vestment of the “spermocarp" of chara is called a up some parts of the subject practically, we must remind “pericarp," and the pro-embryo a “prothallium” (pp. 88 him that a wider knowledge than this implies is advisable and 89). The description of karyokinesis (p. 108) does before attempting to write a book on general biology. not show much knowledge of recent observations. On After reading the preface and introduction, one is led to P. 90, line io from top, the word "sexual” has by an expect that the high ideal set up by the author as regards oversight been printed as "several." The oosphere is actual personal observation would at any rate have led confused with the fertilized ovum on p. 133, although the him to examine carefully and accurately all the types term oosperm is correctly used on previous and sub- described ; it is very disappointing to find that this has sequent pages. The description of the part played by not been the case. In conclusion we venture to repeat the nucleus in the processes of reproduction and con- | Darwin's advice as quoted on p. 200 of this book: “ Give jugation in vorticella on pp. 211 and 212 is somewhat full play to your imagination, but rigidly check it by testincomprehensible. One gathers on pp. 220 and 221 that ing each notion experimentally.” it is comparatively easy to distinguish the nerve cells in

W. N. P.

AN'T HOFF'S “ STEREOCHEMISTRY." attached to an asymmetric carbon atom-thus, by sub

stituting successively different homologous radiclesStéréochimie. Nouvelle Edition de “Dix Années dans l was found possible to produce a concomitant variations

l'Histoire d'une Théorie.” Par J.-H. van't Hoff. the rotatory power of the compound, to make it increzy Rédigée par W. Meyerhoffer. (Paris : Georges Carré, or decrease at will, and even to change its sign. This 1892.)

variation is shown in ascending the series of the esters THE second edition of this work was very fully re-, of tartaric acid and its di-acetyl and di-benzoyl derira

viewed in these columns in 1887 (vol. xxxvii. p. 121), tives. But whereas the weight of the alkyl-group in the and we will therefore content ourselves with noticing esters determines the amount of the rotatory power, as briefly the new matter contained in the present edition, such influence can be perceived in the case of the metallic

We must, however, premise that the stereochemistry salts of tartaric acid, all of which display in solution the of the carbon compounds is based on the assumption same rotatory power, irrespective of the atomic weight of that the four monad atoms or groups satisfying the four the metal. The clue to this anomaly is furnished by the affinities of a carbon atom are situated at the solid angles electrolytic dissociation theory of Arrhenius, according to of a tetrahedron, the centre of which is occupied by the which the dissolved salts are present in the form of their carbon atom itself, and on the allied conception of the dissociated ions, so that, in the case of the dissolved "asymmetric" carbon atom--" asymmetry” arising when metallic tartrates, it is the ion CO (CHOH).CO, which is the four attached atoms or groups are dissimilar, in which alone responsible for the rotation. Arrhenius's theory case two enantiomorphic arrangements are possible for thus receives striking confirmation from an unexpected any given set of four such atoms or groups (see the quarter. notice already referred to). In the first French edition, The subject of compounds containing closed chains i which bore the title “La Chimie dans l'Espace," the fully discussed in the present edition, and the * cis" and author discussed the greatly increased possibilities of i “trans” isomerism discovered by von Baeyer is de isomerism to which this new theory led. Since then | scribed. chemists have used the theory as a guide in the search The relative position of the substituting groups in the for cases of isomerism, and numerous new isomeric com- , stereo-isomerides is also discussed. pounds have been discovered, the existence of which The concluding chapter deals with the stereochemistry could not have been predicted as long as the old con- of nitrogen-a question which had not emerged when the stitutional formulæ written in one plane were employed. previous edition was published. Some of the information The history of this branch of organic chemistry has, given under this heading is rather meagre ; but doubtless during the past seven or eight years, been one continuous the omissions are intentional and they are largely comtriumph for the theory. One of the most striking proofs

pensated for by a very complete bibliography of tbe of the value of these stereochemical views is to be found subject. in Emil Fischer's well-known researches on the sugar

The work is in every sense authoritative, and we cords. group. In the group of the glucoses of the aldehyde

ally recommend it to all interested in the most recent alcohol type, for example, the presence of four asym- developments of organic chemistry.

F. R. J. metric carbon atoms has to be assumed, and the theory predicts the existence of no fewer than sixteen isomerides with a normal carbon chain, as compared with the one

OUR BOOK SHELF. form admissible under the older view. Several of the

Die Fossile Flora der Hottinger Breccie. By R. von predicted forms have been prepared, and the relative!

Wettstein. With 7 plates. (Vienna : Imperial Print distribution of the positive and negative asymmetric i ing Office, 1892.) carbon atoms within the molecule has been determined | THE Höttinger Breccia is a formation about 50 feet by E. Fischer. This and other work confirmatory of the i thick in the neighbourhood of Innsbrück, and situated theory, is described and discussed in the present volume. , about 1200 metres above sea-level. The upper part con.

The theory of the asymmetric carbon atom owes its sists of about 35 feet of coarse conglomerate, with fossils origin to the difficulty of otherwise explaining the optical | chiefly confined to a bed some 3 feet thick, while the

remainder is occupied by alternating beds a foot or two rotatory power of various organic compounds. Quite

in thickness of white or reddish sandstones and breccias, recently, P. A. Guye has suggested that the numerical

which are for the most part very fossiliferous. It has value of this optical rotatory power is dependent upon | been well known to collectors of fossil plants for upwards the relative masses of the substituting atoms or groups of thirty years, and though at first regarded as of tertiary attached to the asymmetric carbon atom, and that if two age, is now uniformly recognised as quarternary, possibly of the four different substituting radicles are of equal , inter-glacial, or more probably post-glacial. The lower

part is characterised by the occurrence of many herbaceous mass the rotatory power will cease. He was unable to

plants, such as the violet, strawberry, coltsfoot, Prunella, verify this view in all strictness, since, in the cases of this &c., which are replaced above to some extent by Cornus kind which he studied, such as that of methyl-ethyl- sanguinea, Rhamnus Frangula, an alder, willow, &c., inaldehyde (C,H) (CH) CH(COH), in which C, H, = COH dicating, perhaps, a change in the forest growth without = 29, there was optical activity. The probable explana. necessarily implying any considerable interval of time tion is, that, as suggested by Guye, not only the masses i

The flora is almost wholly of existing species, and in the

main does not differ essentially from that which might be of the groups, but also the interatomic distances, of 'found in a similar situation at the present day : but six of which the atomic volume is a measure, come into play the species no longer fiourish at such an altitude, and a here. However, by varying the weight of a given group few others, like the box, are absent in Northern Tyrol,

while there are also indications in the relative sizes of the but their definitions will be found in the appendix ; we leaves of others that the climate was milder. Perhaps are afraid, however, that the suggestion that their values the Alps were less elevated and the sea nearer at the time, for certain angles should be committed to memory is not but interest is given to the problem by the undoubted a wise one.

G. A. B. presence of Rhododendron ponticum, which at present only flourishes in a much warmer climate far to the east,

- - -- - - - but, from its discovery in other localities, was evidently

LETTERS TO THE EDITOR. thoroughly indigenous in the Alps. The author regards che fiora as a relic of the steppe-flora " which then spread [The Editor does not hold himself responsible for opinions exover the greater part of Europe, and of which numerous pressed by his correspondents. Neither can he undertake traces still exist, especially in Switzerland and Lower to return, or to correspond with the writers of, rejected Austria, where plants of Oriental facies, such as the yew,

manuscripts intended for this or any other part of NATURE. box, holly, Ephedra, Sumach, hornbeam, feather-grass,

No nolice is taken of anonymous communications.] maidenhair, &c., are its lingering remains.

The Glacier Theory of Alpine Lakes. The work is carefully prepared, doubtful determinations, except in the case of the Arbutus and a new buckthorn

The letter of the Duke of Argyll against the theory of the

formation of alpine lakes by glacial action shows such an amount allied to Rhamnus latifolia of the Canaries, are eschewed,

of misconception of the theory itself, and so completely ignores and the photographic illustrations, pencilled over by the the great weight of evidence in its favour, that a few words on artist, are extremely satisfactory.

J. S. G. I the other side seem desirable.

The Duke says that glaciers “do not dig out," do not "act Observational Astronomy. By Arthur Mee, F.R.A.S. like a ploughshare," but, when moving down a slight incline do (Cardiff: Daniel Owen and Co., 1893.)

"scoop," as well as rub down and abrade. No observer of

glaciers has ever stated, so far as I know, that they do "dig THIS small book should serve the purpose for which it is out,” and it is equally erroneous to say that they “scoop,” for issued ; the object being to provide the beginner with an , that implies that it is the end of the glacier that acts. But the inexpensive treatise to enable him to become familiar with end is its weakest point, where it is melting above and below, and interested in the practice of observational astronomy. and where consequently it can do practically nothing. The For this reason the author limits himself to the purely

whole action of a glacier is a grinding action, and its grinding descriptive side of astronomy, dealing with the sun,

power is greatest where it is thickest, and where, consequently, planets, comets, and meteors, giving numerous references

it presses on the rocks with the greatest weight. The result of

this grinding is seen in the muddy stream issuing from all existwhere necessary. Short chapters are given on eclipses,

ing glaciers ; while the well-known "till" is the product of the transits, occultations, and "the sidereal firmament,” the

rock grinding mill of ancient glaciers and ice-sheets. latter treating of double and coloured stars, &c. The

Notwithstanding the Duke's disbelief in ice-sheets I venture chapter on the telescope contains many practical hints, to think that their former existence has been demonstrated both besides pumerous woodcuts, while that devoted to the in Scotland and Ireland ; but leaving this point, I wish to make moon is very pleasant reading, and gives a good account a few remarks on the extreme inadequacy of the earth-movement of the more general features. The illustrations, as will theory to account for the facts. In the first place it is certain be gathered from the above, are very numerous, many of that no alpine lake can possibly have a long life, geologically them being from the pen of the author himself. With speaking. In the course of a few thousands of years, certainly respect to these, we must add that the one given on p. 72 of

in less than a hundred thousand, all alpine lakes would be filled the Orion nebula does not remind us of the most beautiful

up by the sediment brought into them. It follows that all the object in the heavens, while on p. 66 Donati's comet is

existing lakes must have been formed about the same period, and

that, geologically, a very recent one, and corresponding approxidepicted minus the two long streamers which made this

mately with that of the well-known glacial epoch. But if these object so striking. The book concludes with a short

lakes were all formed by earth movemenis, either just before the obituary of the Rev. T. W. Webb and an appendix con

glacial epoch came on, or during its continuance, or afterwards taining brief contributions from Denning on comets and

we have to explain the remarkable fact that such movements meteors, Gore on variable and temporary stars, Seabroke only occurred within the limits of glaciation, 'never beyond on double star measurement, and a few others.

those limits. In Wales, Cumberland, and Scotland, in the Alps, W. J. L. 1 in Scandinavia, in Finland, in the northern United States and

Canada, in Mongolia and Thibet, in Tasmania and New Mechanics and Hydrostatics for Beginners. By S. L.

Zealand, we have thousands of rock-basin lakes, amid palpable

" | signs of glaciation. But the moment we pass beyond the Loney, V.A. (Cambridge University Press, 1893.) i glaciated districts, mountain lakes abruptly cease. There are This is the latest addition to the series of elementary | hardly any in Spain, none in the Great Atlas, none in Sardinia text-books recently launched by Mr. Loney. The same

| or southern Italy, except in the volcanic areas and away from high standard of excellence is maintained, and the author

| the mountains, none in any of the West Indian islands with

their fine mountain-ranges, none in the peninsula of India or must again be congratulated on his efforts to place in the

in Brazil. And there is exactly the same distribution of fiords. hands of a beginner a book which will give him correct wa

correct | We have them in Norway, in West Scotland, in Alaska, in ideas of the laws and principles which are included in a : South-West America, and in New Zealand, all characterised study of mechanics.

by deeper water within than at their outlets, and all in glaciated It consists of three parts, statics, dynamics, and hydro- ' countries, but nowhere else in the world. statics, each part containing the usual chapters. If the Now it is simply impossible to believe that at a very recent reader should fail to understand the chapter on the laws' period there should have been earth-movements of such a charof motion, he must attribute it either to his want of ability acter as to produce lakes, but always in glaciated districts and or the nature of the subject, for we fail to see how the never beyond them, unless the movements were a result of the author could improve his remarks on this part of the glaciation. This has not, I believe, been yet suggested ; but, subject. We are glad to observe that the words “rate of

in view of the modern theory that any considerable loading of change" find their way into the statement of the second

the surface produces subsidence, it is at least a possible explana

tion. But there are some important facts that seem more in law, for its definiteness is increased thereby. More than

favour of the grinding out of the lake-basins by the enormous the usual care appears to have been devoted to the

weight of ice accumulated over their sites during the height of selection of suitable examples ; some of them, are ex

the ice-age. Looking at a geological map of the Alps it will be ceptionally good, and thus add to the usefulness of the seen that most of the lakes are more or less bordered by tertiary book. Occasionally the trigonometrical ratios are used, or secondary rocks. Lakes Annecy and Bourget are in miocene

and eocene; the lake of Geneva on the north side is miocene of debris still brought down may well have filled up and or jurassic; the lake of Neuchatel, miocene ; lakes Thun and gether obliterated them. The absence of lakes in certain val: Brienz, eocene or jurassic; lake Lucerne, eocene and miocene; cannot be considered an argument of any value call is lakes Zug and Zurich in miocene; lake Constance miocene; ascertained by borings that none have been formed and filleda lake Maggiore is mostly in gneiss, but it is very suggestive again. It must also be shown that the whole conditions ; that it is here comparatively shallow, but becomes suddenly such as to produce that amount of differential grinding cor', deeper and reaches its maximum depth in its lower portion without which no lake can be expected to have been forme! where it is bordered on the east by the jurassic beds ; lake It certainly seems to me that all the facts, all the probabilitis Como also has its greatest depth in triassic rocks, the upper all the converging lines of evidence, are in favour of the gic portion, where gneiss prevails, deepening gradually southward theory, to which the only serious objection is the assam 7 a as in a submerged valley. Equally suggestive is the fact that in that glaciers cannot move uphill. But that they can do se, E. the eastern Alps of Tyrol and Carinthia, where gneiss, porphyry, have done so, is now admitted by most students of gæc and the older stratified rocks prevail, and where glaciers are not motion. Mr. Jamieson, and other Scotch geologists, now so extensive, there are hardly any lakes, except on the i proved that glaciers, over 2000 feet thick, have travelled northern borders, where a considerable number occur in eocene, lateral valleys, and up the slopes of many hills and monclas cretaceous, jurassic, or triassic formations.

and when we consider that the Rhone glacier was 5000 for These various facts as to the distribution of alpine lakes thick just above the lake of Geneva, and more than 2000 ft their almost total absence in all parts of the world outside of thick where it abutted against the Jura, we can have no difc. glaciated districts, and within glaciated districts their prevalence in admitting that it might have travelled up the very sem in the newer and more easily denuded rocks—are what have to slope of the lake bottom, which appears to be less than 100 be explained by the advocates of the theory of earth-movements, in a mile in its steepest parts. ALFRED R. WALLAC and this, so far as I am aware, they have never attempted to do. Equally important, and equally difficult to explain on the earthmovement theory, is the fact that alpine lakes are almost always

Waves as a Motive Power, situated just at those spots where, by means of converging HAVING frequently observed the swimming motions valleys, the glaciers would become heaped up and attain fishes in our Aquarium-and occasionally of porpoises in their maximum thickness, or where there is good evidence that open sea- I have tried to make use for propelling boats ría they have been very thick ; and it is the grinding power of this same principle of locomotion, as exemplified particularly e': enormous weight of ice, acting differentially as regards the softer tail-fin. and harder rocks, that has worn out hollows in pre-existing I fixed a fin (blade) of elastic material like a heim to the valleys now occupied by lakes. In almost every case, too, it of a canoe ; moving that fin laterally to and fro, the same will be seen that there is a constriction or narrowing of the forwards. I have since learned that this "motor* * * valley towards or beyond the lower end of the lake, which, by already twenty-five to thirty years ago by Ciotti, a Sicilia: preventing the free escape of the ice, has increased its thickness of course only an exact version of the method of scalling and grinding power.

one oar, familiar to all boatmen. Whilst trying my CaDeL In the presence of such important series of facts as those here models of boats I soon became convinced that a boat ozgu referred to, mere opinions, or even small and detailed cases of move forward if elastic fins are fixed to it, directed backsdifficulty, can have no weight; but there is yet another considera in such a manner that their flat sides are pressed tion, which most geologists will admit is antagonistic to the the surrounding water, when the boat rolls and pitches 23 earth-movement theory. The whole tendency of geological elastic fins, whilst overcoming the resistance of the are observation is in favour of the usually very slow rate of earth curve like the fins of a fish, driving the water backwards movements, while it is equally in favour of the comparatively consequently pushing the boat forwards. rapid action of denudation by running water. But in order that The canoe was provided with two horizontal fins at the 2 earth-movement could form a lake, it would be necessary that and two vertical ones at the keel, total surface 02 51 the rate of elevation or depression should be so great that the metres ; speed against rather sharp wind and waves estil river could not keep pace with it by cutting down its channel ; at 25 metres per minute. I was unable to take exact Dess and, considering that all the rivers in question are rapid moun. | ments, as the canoe was accidentally sunk before the exper: tain streams carrying great quantities of sediment, this will be was complete. admitted io be a very improbable supposition. But when we I then provided another boat, three metres long, at edhe add to this the still greater improbability that such rapid earth the two pointed ends with a horizontal fin (later ! movements have occurred in scores and hundreds of cases, all and at the keel with two vertical fins; these were all mac at about the same time, geologically speaking, and all just in steel sheet, 1-0.8 mm. thick, subsequently replaced those spots where it can be shown that daring the glacial period aluminium bronze. The boat covered, against a gentle ses a ice must have accumulated, and where the rocks were of such a wind, the distance of 900 metres in 25 minutes. Parim character as to admit of being ground away ; and yet further, fins obliquely the boat turned towards the right or left ; due that no similar earth movements producing similar results have one group of the fios forward, and another of equal a recently occurred in any part of the globe beyond the limits of backward, their action was paralysed, and in similar 92glaciation, the whole assumption becomes so hugely improbable it was easy to make the boat turn round on the spot or to 21 as to render the theory of lake-formation by ice-grinding easy in backward. comparison.

The changing of the surface of the fins (0'3 to 06 $ = Sir Charles Lyell considered that the gravest objection to the metres) caused very little difference in the speed proces glacial.erosion theory was the entire absence of lakes where The same movements of the boat take place is the rods: they ought apparently to exist; and he instanced the valley of I caused artificially. Aosta and the Dora Baltea, the glacier of which produced the I undertook a series of trials, in which I wish to acksos enormous moraines of Ivrea. The valley of the Rhone above with thanks the kind assistance of Mr. Nelson Foley. The Martigny may be adduced as another example of the result was that the rolling yields so little power, (VEIT absence of lakes where they might be expected. But this energy being sufficient to prevent rolling,) that the vertica kind of difficulty will apply to many other valleys, and can only as a source of power may be nearly neglected in the air be answered by general considerations. In both these cases the tions. valleys are comparatively broad and open, and have a rather As to pitching, the power resulting from the action.'. rapid descent. It is probable, therefore, that the ancient glacier waves against gravity is proportioned to (weight of bo' in both was of a nearly uniform thickness, so that its wear crew) x (number of undulations) (height of waves Ba: * ing action on the floor of the valley would be tolerably small portion of the energy developed in moving the bo uniform. To produce a lake we require essentially a dif and down acts upon the fins (surface of boat in water-libe ferential action. There must be much more rapid square metres, surface of fins 0-3 to 0.6 square metres degradation in one part than in another, due either this remaining available force a considerable portion 3 to greater ice-accumulation or to soster rocks in one part the low efficiency of the fins. Supposing, for the sake at than in another. In both the valleys referred to there is much ment, the efficiency to be 25 per cent., the propelling uniformity in the rock-formations throughout, and even if some in a moderate sea works out to the fraction of a mans pas lakes or chains of lakes had been form.ed, the enormous amount Considering these circumstances it seems doubtful, evo

considerable rocking and using boats of more advantageous Besides panmixia and emigration of the more perfect-eyed orms than mine, if it will be possible to have a much higher individuals, as explained by Prof. E. Ray Lankester, allow me peed ihan 2000 metres per hour. It appears also that the to suggest another cause for the dwindling of the eyes in caveivailable force will be hardly sufficient to struggle successfully dwelling animals. igainst strong winds and currents.

Prof. Weismann says that the degeneration" can hardly be of I do not therefore prognosticate too confidently any practical direct advantage to the animals, for they could live quite as well alue to the motor, but should be very glad if some of your | in the dark with well-developed eyes.” I submit, however, that eaders would inform me as to any similar experiments which in a place permanently dark the eye is not merely useless, but, pay already have been made.

"H. LINDEN. as a delicate and vulnerable part, it becomes a positive source Zoological Station, Naples, February 19.

of danger to the animal. No longer helping the creature to

avoid obstacles or danger, it is, in proportion to its size, exposed Blind Animals in Caves.

to injury, destructive inflammation, and the attacks of parasites As a reader of Mr. Herbert Spencer's writings and a disciple

in a manner which must not seldom lead to the death of the his, I shall be very glad to lift Prof. Lankester's glove. In

individual. As other senses become more acute, and the eye he first place I would point out that the process he describes is

recedes, this danger diminishes, and when the eye has become ot natural selection in the ordinary sense ; natural selection is

a mere rudiment, “hidden under the skin,” its presence ceases he deaih of the unfit and the survival of the fittest. In the

to be a disadvantage, and so degeneration does not proceed to aggested process neither the animals with perfect eyes, nor those

complete suppression. ruth imperfect, are destroyed in the struggle for existence; they

It is a wonder that Mr. H. Spencer should have overlooked

Prof. Lankester's explanation, for the English editor of Prof. re simply segregated. But this is of minor importance. The uestion is whether there is any foundation for the hypothesis

Weismann's fifth essay has not failed to call attention to it.

Mirfield, February 27. iggested.

A. ANDERSON. Prof. Lankester supposes that the individuals born with delec

[Darwin has himself drawn attention, in regard to burrowing ve eyes have remained in the dark places, while those with

animals, to the conditions pointed out in the above (" Origin of erfect eyes have followed the glimmer of light and escaped.

Species,” 61h edition, p. 110).—ED.) ut he has overlooked the fact that blind cave-animals re born or hatched at the present day with well-developed

Foraminiser or Sponge ? tes. It is clear, therefore, as in every other case to which se law of recapitulation applies that the variations I AM glad to find that Mr. Pearcey agrees with me in regardI which the evolution is due occurred at a comparatively late ing Neusina Agassizi, Goës, as identical with Stannophyllum eriod in the life of the individual. Why did not all the indi. zonarium, Hæckel. But with respect to its systematic position duals escape when they were young, and could still see with I do not as yet see sufficient reason to differ from Prof. Hæckel at spectacles? When the imperfection of the eyes did occur, in regarding it as a sponge, although I have never observed hat ground is there for assuming that it was a congenital flagellated chambers and cells any more than he. The large triation ? It seems to me perfectly certain that it was a masses of foreign bodies always present in this organism offer terioration of the eyes caused by the fact that the individual very serious difficulties in sectionising it, and as long as we are id lived in the dark all its life. In short, I hold that the law not absolutely certain about its cellular structure we are justirecapitulation in development, the law of metamorphosis, or

fied in thinking with Hæckel that general appearance and the ogenetic law, as Haeckel called it, is itself a sufficient proof of presence of oscula, pores, subdermal cavities, horny skeleton, e inheritance of acquired characters. This argument has never

&c., are sufficient to characterise the form as a sponge. en met or even considered by any of those who talk of con Mr. Pearcey mentions six genera of Foraminifera which he nital fortuitous variations without defining them.

thinks approach closely to Slannophyllum. I am sorry I cannot The evidence for the statement I have made is, I confess, not

see much similarity. The chitinous lining in the tube-like body uite complete, but it is sufficient for my present purpose. In

of some Foraminifera certainly bears not the sligbtest resemmper's " Animal Life," p. 80, there is an account of Pin.

blance to the distinct fibrous stroma of Stannophyllum, which Theres Holothuria, based on the author's direct observations. reminds me much more of the filaments of the true horny sponge his species lives in the respiratory trees of Holothurians, and

Hircinia. If anything tells in favour of Mr. Pearcey's view, it the adult the eyes are degenerate and invisible on the exterior is the concentric lines of Stannophyllum, which recall the forathe animal. The young is hatched as a zoæa with perfect miniferal rather than the sponge type of growth. pical eyes ; even when it enters the host it retains its eyes, but

The final decision of this question can of course only be erwards the eyes degenerate and become covered over by the | expected from an examination of the cell structure. rapace. In the common mole, to take an instance among

University College, Liverpool,

R. HANITSCH. ammals, the optic nerves are degenerate in the adult, so that

February 25. ere is no connection between eye and brain ; but in the ibryo both eyes are connected with the brain by well-developed

A Magnetic Screen. tic nerves. I am not at present acquainted with any obser. tions on the young of Proteus, or the blind fish Amblyopsis, DURING the last vacation St. John's College, Oxford, has the blind Crayfish of the mammoth cave, but I am quite con been lit with the electric light, and a transformer of the dynaent that the young in all these cases have relatively well momotor type, weighing over seven tons, has been placed within veloped eyes. At any rate Prof. Lankester to support his theory about sixty feet of the electrical testing room of the Millard ist prove that they are blind from the beginning ; for if they are Laboratory, which is furnished with several reflecting galvano. I then it is clear that the variations which we have to consider meters. I greatly feared that the instruments would suffer much k place during the life of the individual living in the dark, and from the magnetic field of the large transformer. When it was 2sequently the support of Prof. Lankester's suggestion vanishes. found that no other space could be given up for the machine, of. Lankester again writes of the deep sea as though it were I devised a method of construction which the Oxford Electric destitute of light as the mammoth cave, or the subterranean | Lighting Company very kindly carried out for me when buildme of the Proteus, but this is notoriously not the case. With ing their dynamo house. My method is to construct a wall of

ard to fishes, Dr. Günther says that below the depth of 200 scrap iron round the three sides of the dynamo nearest to our homs sinall-eyed fishes as well as large-eyed occur, the laboratory. The iron wall is about eight inches thick, and is made mer having their want of vision compensated for by tentacular by building two brick walls parallel to one another, and filling ans of touch, whilst the latter have no such accessory organs, the interspace with scrap-iron ; a delicate magnetometer used I evidently see only by the aid of phosphorescence; in the for testing the field at unprotected and protected points equiatest depths blind fishes occur with rudimentary eyes, and distant from the magnets, when the machine is in action and not hout special organs of touch. Dr. Günther mentions fifty: so, shows that the iron wall is an effective barrier to the magnetic . species of fishes living at depths beyond 1000 fathoms, and influence. I venture to make known this method of shielding ong these only three Aphyonus gelatinosus, Typhlonus nasus, off a magnetic field, because in these days of electrical invasion 1 Ipnops Murrayi are blind. It is, I think, sufficiently evident it may be of use in protecting physical instruments from being t the biology of the deep sea is quite different from that of seriously disturbed, and rendered useless for any but the terranean caves or habitats. 1. T. CUNNINGHAM. roughest determinations.

FREDERICK J. SMITH. Plymouth, February 27.

Trinity College, February 28.

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