432 THE ZOOLOGIST. 



NOTICES OF NEW BOOKS. 



A Treatise on Zoology. Edited by E. Ray Lankester, M.A., 

 LL.D., F.R.S., &c. Part IV. The Platyhelmia, Mesozoa, 

 and Nemertini, by W. Blaxland Benham, D.Sc, M.A. 

 Adam & Charles Black. 

 All serious students of zoology — to whom this publication is 

 addressed — will welcome the appearance of another volume of this 

 excellent treatise. The present contribution is written by Dr. 

 Benham, and was mostly completed before the author left England 

 to take up his appointment in the University of Otago, New 

 Zealand. The Platyhelmia represent a natural phylum often 

 submerged by writers under the old and more inexact term 

 "Vermes," and comprise Flatworms (Planarians), with their 

 offshoots, the Flukes and the Tapeworms. A method pursued, 

 as in the previous parts — already noticed in these pages — and 

 again one of the original features, is an historical survey of each 

 class, showing the slow and gradual accumulation of the facts 

 and theories dealt with, and the chief zoologists who have con- 

 tributed to our knowledge of the group. One of the most 

 interesting questions raised in the volume relates to the Tape- 

 worm, and as to how the life-cycle of these animals, now perfectly 

 understood, conforms to, or illustrates Steenstrup's Theory of the 

 Alternation of Generations. This is very fully discussed, and 

 demands the careful study of those interested in the question. 



It is still apparently too often forgotten that it is in such 

 books as the one under notice, and in studies such as it enforces, 

 that the true facts of evolution are to be found, and not by 

 surface impressions or ingenious suggestions. Nothing seems so 

 much in vogue as an acquiescence in the dogmas of a popular 

 evolution designed for the instruction of the man in the street, 

 or for those who like to acquire new ideas on trust. It is, how- 

 ever, probably as true as the facts of evolution itself, that in 

 every civilized country the number of those who have acquired 



