323 



their surroundings. The general structure, classification and 

 strange metamorphoses of Crustacea are indeed ably dealt with in 

 three preliminary chapters, but the principal portion of" the book 

 is devoted to a review of the Crustacean communities character- 

 istic of the sea shore, the ocean depths, the high seas, fresh-waters 

 and the land, while three concluding chapters treat of Crustacean 

 parasites and messmates, Crustacea in relation to man and the 

 Crustacea of the past. As may readily be imagined, the descrip- 

 tion of the wonderfully varied forms included in the foregoing 

 categories suggest numerous problems of much scientific and general 

 interest, and it is an excellent feature of the book that these 

 problems receive a good deal of attention. 



With a book so crowded with interesting matter it is obviously 

 impossible in a short notice to do more than refer somewhat 

 arbitrarily to a few of the points touched upon. Thus, special 

 attention may be called perhaps to the chapter on the floating 

 Crustacea of the open sea in which we get much general informa- 

 tion about the plankton and its relation to the higher marine 

 animals such as the fishes and whales. The closeness of this 

 relation is summed up in the striking phrase "all fish is diatom," 

 the words being used in the same physiological sense as those in 

 the biblical generalisation " all flesh is grass." It follows that 

 the study of the plankton, a very large proportion of which con- 

 sists of microscopic Crustacea, is of great practical importance as 

 well as scientific interest. 



Many examples of the extraordinary modifications of structure 

 in pelagic Crustacea are given, and the exceeding transparency, 

 brilliant coloration, and marked phosphorescence of certain species, 

 also form subjects of special comment. In connection with the 

 question of transparency, doubt is thrown on the idea that this is 

 to be regarded as a protective adaptation because of the fact that 

 some larger animals, such as the herring and Greenland whale, 

 swallow the plankton wholesale. In support of the usual view it 

 may be suggested, however, that the main struggle for existence 

 with these plankton organisms is not between them and such 

 creatures as fishes and whales, but between themselves, and that 

 consequently transparency as such may be an extremely useful 

 character. In any case it can hardly be claimed that the indis- 

 criminate consumption of plankton Crustacea, etc., by fishes and 

 whales furnishes an argument against protective adaptations 



JouRN. Q. M. C, Series II. No. 69. 22 



