SOME NEW BOOKS. 



Outlines of Zoology. By J. Arthur Thomson, M.A., F.R.S.E. 8vo. 

 Pp. 641. With 32 full-page Illustrations. Edinburgh: Young J. Pentland, 

 1892. Price I2S. 6d. 



The number of text-books of Zoology increases rapidly year by 

 year. Only a very short time back the difficulty was to hnd a book 

 of any kind, written in English, which gave an adequate account of 

 general Zoology and the Comparative Anatomy of Invertebrates as 

 well as Vertebrates. Nowadays, the difficulties are just as great, not 

 on account of the paucity of books, but by reason of their very large 

 number, good, bad, and indifferent — particularly of the last two 

 categories. The struggle for existence among these text-books must 

 be very keen, especially among those which are merely cram-books 

 for examinations of the universities of London and other places. 

 On the whole, the more favourable varieties appear to thrive, though, 

 unfortunately, the rest do not become extinct. 



The problem which has to be solved by anyone who writes a 

 book of this kind at present is how to pay due attention to the 

 " types " without producing a mere cram-book. An elementary 

 text-book, in which these types were treated with too scant courtesy, 

 would die a rapid death. Mr. Arthur Thomson, in the manual 

 before us, seems to have succeeded in striking the mean between 

 a too exaggerated respect for the type system and a too pro- 

 nounced contempt for it. Those animals which find a place in 

 the schedules of universities are for the most part carefully 

 described. We are glad to notice that 12! pages are devoted to an 

 account of the structure and development of that important creature, 

 the earthworm ; the leech, however, only gets 5^, perhaps rather too 

 scanty an allowance. 



Besides these descriptions of representatives of the different 

 groups of the animal kingdom, there are good general summaries of 

 the characters of the groups themselves. The Mollusca will serve to 

 illustrate the method adopted. First of all the three main divisions, 

 i.e., Lamellibranchiata, Gasteropoda, and Cephalopoda, are men- 

 tioned, with a remark enclosed in square brackets to the effect that 

 Dentaliiim is to be placed in a separate class, and that some 

 authorities admit a few other small classes. Then follow the 

 " General Characteristics of Mollusca," and a tabular classification. 

 After this are " General Notes on Molluscs," containing a few words 

 on the signification of the term " Mollusca " as used in the classi- 

 ficatory schemes of Linnaeus and Cuvier ; some additional 

 observations upon the structure and growth of the shell ; and some 

 remarks upon the larval forms. Each class is then treated in a: 

 somewhat similar fashion, the general characters preceding the 

 detailed description of the type, and a classification following. 

 Although this is the general plan upon which the author proceeds, 

 the treatment of each group is not detail for detail the same. This, 



