412 



NA TURE 



[August 29, 1895 



supials enter the scheme, but it may be mentioned that 

 the loss of the primeval carapace of ordinar>' mammals 

 is attributed (p. 209^ to a deficiency of carbonate of lime 

 in the water and plants on which they subsisted. It will 

 also be a surprise to zoologists to learn (p. 142) that the 

 coloration of the Indian black-buck is due to its having 

 lost its armour on the ventral sooner than on the dorsal 

 surface. And equal wonderment will be experienced 

 when they read (p. 300) that dolphins are near relatives 

 of Plesiosaurs, and that the author doubts whether 

 " there are any good reasons for supposing that 

 Ichthyosaurs were nol mammals" I 



In another chapter the author is led, from the study of 

 monstrosities, to the conclusion that horses are more 

 nearly allied to the Artiodactyla than they are to either 

 rhinoceroses or tapirs 1 



Many more similar instances might be quoted, but it 

 will suffice to say that if the author be right, all zoologists 

 are hopelessly in the wrong in their views on mammalian 

 affinity. 



Among the redeeming features in the book will be 

 found many interesting obser\ations on the coloration 

 of cats and horses, and the author appears to have made 

 out a fairly good case for the derivation of the striping 

 of the tiger from the spots of a leopard-like type. Many 

 of the figures of animals, especially the skins of leopards, 

 are admirable examples of photography, and would be 

 well worth reproduction in other works. 



R. LVDEKKER. 



OUR BOOK SHELF. 



Le Cause DelF Era Glaciale. By Luigi de Marchi, 

 Libcro Docente di Meteorologia nella R. Universita 

 di Pavia. (Pavia: Fratelli Fusi.) 



This work does not fulfil the expectations raised by 

 its title. It is a prize essay of 220 large octavo 

 pages, divided into three sections. The first treats of 

 the climatic conditions of a glacial invasion, and here 

 the author agrees with a number of German writers 

 whom he quotes, in considering that a glacial epoch is 

 due to a lowering of mean animal temperature and a 

 diminution of the annual range,- accompanied by an 

 increased rainfall in summer. The next section treats 

 of the temperature of the air. \Vc find a large collection 

 of empiric fonnuUe, taken for the most part from German 

 authors, some of which arc based on assumptions which 

 appear to be far from satisfactory, and which certainly 

 cannot be verified in the exhaustive way which one would 

 wish before applying them to find the lemperalurc in the 

 Glacial Age. Among these there is one more important 

 than the others, in which /, the mean annual temperature 

 at any given locality, is expressed in terms of no less 

 than fifteen physical quantities, such as the supposed 

 temperature of an ideal sky,' the absolute radiating power 

 of this sky, the transmissive powers of the atmosphere 

 for radiation from earth and water, and for sun-he;it, and 

 last, but not least important, "a tcnn of correction which 

 expresses the cfiect of the physical and meteorological 

 condition of the locality," and this term may, according 

 to the author, oscillate between - 6' C. and -(-6' C. 



The third section, entitled "The Cause of a Glacial 

 Age;," contains the author's deductions from this fonnula. 



I ■ 



Krfili 



liu( (following Pouillcl, 



'.ICC, of which ihcradiat- 



' , and of all the celestial 



equal 10 — 45'*4 C. for 



NO. 1348, VOL. 52] 



He uses it to disprove the hypothesis that the Ice .Age 

 was due to a change in the obliquity, but he cannot 

 apply it to discuss CroH's theory, because it only takes- 

 account of the total annual heat received. Hence he 

 refers to previous writers for his criticism on Croll. 

 Similarly the geographical hypothesis is dismissed as 

 insufficient, so that the way is cleared for the author's 

 own hypothesis, viz. that the Ice Age was caused by a 

 general lowering of temperature which arose from a 

 diminution of the atmospheric transparency, which can 

 only be explained ^p. 183) as the effect of a general 

 diffusion into the atmosphere, over the whole surface of 

 the earth, of a gas, vapour, or dust which absorbs, or 

 reflects towards space, a part of the heat which comes 

 from the sun. " But since the glacial epoch also pre- 

 supposes .in extraordinary rainfall, among the many 

 hypotheses which may be framed, one spontaneously 

 presents itself, viz. that a great mass of aqueous vapour 

 was launched against and diffiiscd into the atmosphere." 

 Owing to the lowering of temperature due to want of 

 transparency, the vapour would fall as snow, and this 

 precipitation would go on until the mass of vapour 

 injected into the atmosphere is entirely or in great part 

 eliminated. 



The author quotes an Italian writer, who suggests 

 that the action of volcanos in the age preceding the Ice 

 .Ages affords a possible explanation of the (supposed) 

 launching of these vast masses of aqueous vapour into 

 the atmosphere. 



Lcitfadcn fiir Itistologische Untcrsudiungcn. B)- Bemhard 

 Rawitz. Second edition. (Jena : Gustav Fischer, 

 1895.) 



HisTOl.OGic.M. methods have become so perfected, 

 microscopic appliances so modified, and staining reagents 

 so numerous, that it is necessary to have good reference 

 books for use in laboratories. .Mthough there are .a 

 number of such works, amongst which we may mention 

 Lee's " \"ade Mecum," Sims Woodhcad's " Manual,'' and 

 Fletcher's edition of \'on Kahldcn's " Practical Patho- 

 logical Histology," the appearance of a new edition of 

 Rawitz's compendium will be welcomed by all who were 

 familiar with the first edition, which was published six 

 years ago. It resembles \'on Kahldcn's book in arrange- 

 ment, but while this latter has been compiled specially 

 for pathological in\estigations, Rawitz's "Lcitfadcn" 

 is essentially intended for the biologist and physiologist, 

 and forms a suitable supplement to its morbid counter- 

 part. When reviewing Ur. Fletchers translation of \'on 

 Kahldcn's book, some time back, we regretted the omission 

 of various matters relating to section-cutting, embedding 

 and staining, an omission which is excusable on the 

 ground that in a work on practical pathological histology 

 a sound knowledge of these subjects might lie taken for 

 granted. Rawitz gives excellent descriptions of all our 

 recognised modern methods, and a careful account of 

 paraffin embedding and paraffin cutting, which will 

 prove useful to all who wish to become familiar with what 

 IS undoubtedly the best method for gener.il histological 

 purposes. His directions for working with celloidiii are 

 equally good, and since this method is somcwh.it neglected 

 in this country the beginner will find a nunilicr of hints 

 which Dr. Fletcher might well have inclucled in his trans- 

 lation. The completeness with which the \arious methods 

 of fix.ition, hardening, and staining have been enumerated 

 is .'idmir.'ible, and we gain the firm conviction that the 

 author has only included what is sound, and in careful 

 hands certain to give good and trustworthy results. 

 Chapter xi. (part l) contains some useful information on 

 the art of drawing and "reconstructing" microscopical 

 objects. The " Leitfaden " may be recommended with- 

 out hesitation to the histologist as a Ijook of reference for 

 use in the laboratory : it will save time, and seldom cause 

 disappointment. .A. A. K. 



