October, 1896. SOME NEW BOOKS, 271 



and properties in certain directions. Although, to begin with, each cell 

 has the same nuclear composition, yet the interrelations it holds with 

 its fellows (" centrifugal causes "), and the motive forces due to the 

 action of environment (" centripedal causes"), determine the nature 

 of the cells themselves and the tissues they make up. This idea has 

 been strongly advocated in a later work, " Eine Theorie der Organ- 

 ischen Entwicklung," by Driesch, whose experiments in the mechanics 

 of development led him to similar conclusions. He extends it even 

 further, seeming to hint that all protoplasm is fundamentally the 

 same, and that whether a fertilised egg develops into a man or a 

 medusa is decided by external conditions alone. 



Finally, although the importance of the cell as a morphological unit 

 may to some minds be unduly insisted upon, the comparison in the 

 concluding pages between the development of an egg-cell into a man, 

 and of a man into a member of a state, both depending on epigenetic 

 principles, is a suggestive thought, and contrasts favourably with the 

 cumbersome, if ingenious, comparisons and similes resorted to by the 

 author of " the germ plasm." 



Taken as a whole, Hertwig's doctrine is easier of understanding 

 and application than Weismann's, but what seems to render it 

 infinitely superior to the latter is its capability of being tested by 

 experiment and observation, towards which object much may be done by 

 such work in the department of experimental research as has recently 

 been published by the author, Roux, Driesch, Chabry, Morgan, and 

 others. A word of praise is due to the translator for having effectively 

 rendered the sense of the original with a minimal departure from the 

 text. M. D. H. 



Snakes. 



Catalogue of the Snakes in the British Museum (Natural History). 

 Vol. III. By George Albert Boulenger, F.R.S. Pp. xiv., 727, with 25 plates, 

 and figures in the text. Published by order of the Trustees. London, 1896. 



This volume contains the Viperidae, the Amblycephalidce, and five 

 sub-families of the Colubridae ; the Elapinae, Hydrophiinae, Elachisto- 

 dontinae, Dipsadomorphinae, and Homalopsinae. In bulk it is much 

 the largest of the three, which in part is due to addenda and corri- 

 genda, forty-one pages of which apply to vol. i., and twenty-three to 

 vol. ii. The high degree of merit apparent heretofore is maintained 

 throughout, and the author is to be warmly congratulated for the 

 admirable manner in which he has completed the series. His contri- 

 bution is certainly one of the best that has appeared on the subject, and 

 is sure to result in great advancement of our knowledge of the order. 

 The classification adopted is a decided improvement on previous 

 attempts. Whether ophidiologists generally accept a scheme placing 

 Hydrophidas and Elapidae with the ordinary Colubridae, or which 

 throws together Crotalidae and Viperidee as a single family, will make 

 little difference in the utility of the work. In the midst of so much 

 that is of the best, however, there are points which render it liable to 

 attack, and which will lead to modification in the hands of others, if 

 not in those of the author. Much interference with the names of his 

 genera might have been prevented by rulings somewhat less arbitrary; 

 generic names applied by early writers have been arbitrarily dropped 

 for later ones, and genera have been subdivided out of existence, 

 newer names being given to all the parts. Numerous cases have been 

 ruled out as naked names which are not really such, since with each 

 generic or subgeneric name its author had specified a characteristic 



