4 68 SOME NEW BOOKS [june 



Very useful also would be an exact investigation of the period of life of any 

 organism during which the influence of any agent would prove most effective — 

 whether good or bad — on one system, or function, or organ. 



But no one can read this book without perceiving, by what has been done, 

 what remains to be done ; it is an eminently suggestive work, and therefore it 

 is as well to leave the reader to draw his own conclusions. We earnestly hope, 

 for the sake of biology, that the book will be extensively l-ead by the younger 

 workers : most certainly it will open their eyes to new views, and push them 

 in a field where much is to be done, and a good harvest reaped. Mr. Daven- 

 port deserves the thanks of all who are interested in biology. 



H. de Varigny. 



"KORSCHELT and HEIDER." 



Text -Book of Embryology of Invertebrates. By Drs. KORSCHELT and 

 Heider. Vol. II. (Phoronidea, Polyzoa, Brachiopoda, Crustacea, 

 Palaeostraca. ) Translated by M. Bernard. Revised and Edited by 

 Martin F. Woodward. Pp. xvi. + 370 and 165 figs. London : Swan 

 Sonnenschein and Co., 1899. Price 12s. 



If writing a text-book be a thankless task, the translating of a foreign text- 

 book must be worse. In such a subject as embryology, the functional life of a 

 text-book may be put down as about two years, so that a translation really 

 recpiires to be practically re- written. An attempt has been made by Mr. Wood- 

 ward to meet this want by the addition of footnotes, but we think it would 

 have been better to have taken the bull by the horns and have re-written the 

 whole. In some cases we find that a note by the revising editor at the end of 

 a page or two of "general considerations" leads one to condemn the latter as 

 " premature conclusions." This is specially evident in the first and the last groups 

 dealt with, namely, the Phoronidea and Palaeostraca. From these remarks it 

 will be seen that Mr. Woodward's notes add greatly to the value of the book in 

 bringing it up to date and in reducing the relative antiquity of the work to a 

 minimum. 



A perusal of the discussions upon phyletic affinities leads a thinking 

 zoologist to pause and consider whether zoological science is yet sufficiently 

 advanced for the determination of these relationships. Do we not require to 

 definitely settle what features are to be regarded as of phyletic value ? We find 

 the authors arguing for the unity of the Molluscoida as a natural group, firstly, 

 on account of structural resemblances (pp. 84 to 88) which, if one allows for 

 similarity of habitat, resolve themselves into a well -developed coelom with 

 similarly related divisions. The absence of a true coelom again assists the 

 authors in isolating the Entoprocta though they commence their discussion of 

 the Phoronidea by the remark : — " The Actinotrocha may without difficulty be 

 regarded as a somewhat modified Trochophore." This becomes modified later 

 into (p. 86) " The Actinotrocha type is distantly allied to the Trochophore larva, 

 being distinguished from the latter chiefly by the presence of a true coelom," 

 and this " distant alliance " from Brachiopoda through Actinotrocha to Trocho- 

 phore is used as an argument against the comparison of the former with Sagitta. 

 The structural resemblances between Brachiopoda and Chaetognatha are dismissed 

 as "analogies," and their differences "in manner of life" are quoted against 

 genetic affinity ! Surely structural resemblances combined with differences in 

 habitat would form the strongest arguments for genetic affinity. 



The immense number of facts and observations clearly set forth will place 

 this "Embryology" in a unique position, and the work of translation has been 

 ably and fluently effected. All the diphthongs are abolished, and such words as 

 " zoaea," " coelom," " Palaeostraca," " zooecium," and " caenogenetic " have a 



