52 



NA TURE 



[May 17. 1888 



remove the epidermis from a snail-shell and observe the 

 result. 



The lip or aperture of a snail's shell is not generally 

 called the peritreme but the peristome. The lines of 

 growth in a snail's shell are not "arranged concentrically 

 with the nucleus," although this is the case with the 

 growth-lines in bivalves. 



We fail to understand how the operculum of a snail 

 "differs from the true shell in having more conchiolin 

 entering into its composition." Surely the author meant 

 to say less conchiolin and more chitine ? 



The cpiphragm, or layer of hardened mucus, sometimes 

 strengthened with carbonate of lime, closing the aperture 

 of the shell of land-snails during hibernation is called 

 here also the clausiliwn ! (p. 5). The description of the 

 odontophore with its radula and jaws (pp. 6 and 7) is very 

 inaccurately rendered, and in copying Prof. Lankester the 

 author has carefully also quoted a mis-statement as to 

 the formula of the teeth. 



The eggs of snails are said by the author to be " laid 

 in a string, which is called the nidamental ribbon, or 

 inclosed in horny capsules." This is true of sea-snails 

 such as the whelks (Fusus, Buccinum, &c), but it is not 

 the case in land-snails, of which Dr. Williams is dis- 

 coursing. In these the eggs are separate and protected 

 by a shell, which is sometimes membranous and flexible, 

 at others calcareous and brittle, while those of the fresh- 

 water species are deposited in small glairy masses of soft 

 transparent jelly-like consistence. 



Turning from the snail to the fresh-water mussel (Chapter 

 II.), the author, in describing the animal of the latter, 

 appears to have made a mistake similar to that which he 

 has made with regard to the garden snail : not knowing 

 his subject well, he has in fact described a siphonated 

 Mya, when he fondly imagined he was writing about a 

 non-siphonated Unio or Anodon. 



Turning to the species enumerated by the author, we 

 regret to observe that here the discrimination of the 

 expert is alike wanting. For example, Anodonta anatina, 

 Linn., figures as a good species, whereas it is merely a 

 variety of A. cygnea, Linn. It seems rather absurd to give 

 in a shell-collector's hand-book such shells as Physa acuta, 

 Drap., "Hab. In one of the lily-tanks in Kew Gardens } 

 imported" (p. 72); Bulimus Goodallii, Miller (intro- 

 duced into a green-house with exotic plants) ; Vertigo 

 tumida, Westerlund, another " casual " ; P. dilatatus, 

 Gould, in the canals around Manchester, " introduced 

 from America in cotton bales." If these are admitted, 

 why omit Clausilia parvula and C. solida, also " casuals," 

 which appear both in Sowerby's last edition, and in 

 Gwyn Jeffreys, v. 161-62 ? 



Far too much prominence is given to worthless varieties 

 of the common snail Helix aspersa, such as minor, 

 maxima, albida, and sinistrorsum, &c. ; but, having put 

 them in, why should the author omit such a one as 

 Unio timidus var. ponderosa ? Many of the genera 

 too, need revision to be brought up to date. Thus, 

 Achatinaacicula should be Ccecilianella acicula j Bulimus 

 acutus should be Helix {Cochlicella) acuta j Zonites should 

 be Hyalinia. By the way, Zonites draparnaldi is omitted 

 altogether, although known for years. 



The habitats of many of the species are badly given. 

 Thus, Testacella Maugei is said to be found in gardens 



and fields, whereas it has been met with in the neighbour- 

 hood of Bristol, whence it has spread to a few limited 

 localities. 



Why are the three known localities for Vertigo moulin- 

 siana (p. 129) omitted ? — Itchen Valley, near Otterbourne ; 

 near Hitchin ; and near Rye-House, Herts. Other quite 

 local species are recorded as if they occurred everywhere 

 as Helix pi sana and H obvoluta, &c. 



A few woodcuts are inserted, but they are very poor 

 and not accurately drawn. Testacella haliotidea is 

 reversed. 



The minute characters of the shells, so useful in many 

 instances in the field, are omitted. The book is inter- 

 leaved, which doubles its thickness for field-work, and we 

 at first wondered why so much plain paper was added. 

 It has since occurred to us that the author had the con- 

 venience of the reviewer in his mind's eye, and we must 

 say we found the blank pages most useful in correcting 

 the text as we turned over the leaves. 



Is it too much to hope that the author may be 

 able to give some attention to the living land and fresh- 

 water Mollusca before he brings out a new edition of his 

 handy shell-collector's manual, and so avoid those pit- 

 falls into which he who compiles unskilfully and without 

 practical acquaintance with his subject is sure to slip ? 



OUR BOOK SHELF. 



A Text-book of Biology. By J. R. Ainsworth Davis, 

 B.A., Lecturer on Biology in the University of Wales, 

 Aberystwith. (London : Griffin and Co , 1888.) 



This is one of a class of books which the system of 

 examining the whole world on a limited schedule, drawn 

 up by a Board of disinterested philanthropists, is bound to 

 produce. It will delight the misguided student whose 

 sole desire is " to get through " with the least know- 

 ledge possible, and will disgust every competent teacher. 

 Mr. Davis is in error in stating that his book supplies a 

 gap in literature. The little text-book by Prof. Lloyd 

 Morgan is on the same lines, and appears to us to be far 

 less objectionable, inasmuch as it is, though of smaller 

 dimensions, a more genuine exposition of the principles 

 of the subject, less of a cram-book than the present work, 

 and written with maturer judgment and literary power. 

 The only way to prevent the study of biology, as directed 

 by the University of London, from sinking into a worthless 

 exercise of memory applied to the contents of such little 

 books as this by Mr. Davis, is to change the animals and 

 plants enumerated in the schedule every three years. 

 This, however, would hardly suit the ubiquitous aspirants 

 to a degree for whom alone the Imperial University 

 arranges its curriculum. Nor would it suit Mr. Davis 

 and other more distinguished authors of regulation cram- 

 books. The fact is that genuine education in biology as 

 a science, and the influence of personal contact and 

 association with an active investigator and discoverer as 

 teacher and friend, are destroyed by the Imperial system 

 of schedule and examination ; and their place is taken by 

 weary grinding at little books written by teachers of no 

 authority, and too often ignorant as well as unintelligent. 



Mr. Davis has borrowed a number of excellent figures 

 to illustrate his book, which is nothing more nor less than 

 a strictly limited, and in minor points an inaccurate, 

 description of the types named in the schedule of the 

 University of London. The new figures are bad, and the 

 short general introduction is not merely shallow but 

 erroneous, e.g. the account of protoplasm and the tabular 

 statement of differences between plants and animals. 



