April 7, 1922] 



SCIENCE 



377 



shorter papers which have supplied the first 

 adequate account of the free crinoids. It has 

 been no mean task, for when Mr. Clark tackled 

 the problem, the classification of the comatulids 

 was in a state of hopeless confusion. The reso- 

 lution of this chaos into a system was a brilliant 

 piece of analysis and construction, and consti- 

 tutes a notable achievement in the field of ani- 

 mal taxonomy. The present volume contains 

 an enormous amount of detail, and maintains 

 the high standard of Part 1. It has a wealth 

 of illustration — no less than 1,364 figures, the 

 greater part drawn by the author, as there are 

 few photographs. Such figures as have been 

 taken from previous authors have in almost all 

 cases been retouched by Mr. Clark to bring out 

 points previously overlooked or misinterpreted. 

 Nine hundred forty-nine drawings appear in 

 the text. 



What might be termed the background of the 

 work has been stated by Mr. Frank Springer 

 in his review of Part 1, and need not therefore 

 be recounted here. The present volume con- 

 tains a very large amount of entirely new and 

 original matter. It begins by taking up the 

 description of the radials of the comatulids at 

 the point at which it was left at the end of 

 Pa.rt 1. The articular faces of the radials of 

 52 species are described in detail from dissec- 

 tions preserved in the collection of the National 

 Museum and reference is made to the 20 de- 

 scribed more or less satisfactorily by previous 

 authors. The whole subject of the structure, 

 relationships, physiology and homologies of the 

 socalled post-radial structures (arms and pin- 

 nules) is exhaustively treated. All of this 

 matter is original and is based upon specimens 

 in the National Museum. The perisomic plates, 

 or those developed within and entirely confined 

 to the ventral surface, come in for detailed de- 

 scription for the fli'st time, the subject being 

 handled in an entirelj^ new way; and the side- 

 plates and covering-plates of the pinnules of 

 203 species in the National Museum collection 

 are also treated. 



A complete and detailed account of the an- 

 atomy, embryology, and regeneration of the 

 comatulids is given. There is at present no 

 single source from which this information can 



be derived, as it is widely scattered through a 

 great number of usually short papers in various 

 languag-es. 



The spawning season of 24 species is given; 

 previously that of only 4 species was known. 



The pentacrinoid young of 28 species are de- 

 scribed and the first comparative account of the 

 pentacrinoids is given. 



A considerable amount of information is as- 

 sembled concerning the habits, reactions to 

 various stimuli and food, concerning which up 

 to the present there has been no adequate source 

 of information. 



All of the numerous parasites and commen- 

 sals on the crinodis are listed and when neces- 

 sary for comparative purposes, many of those 

 occurring on other echinoderms. Parasitism 

 and commensalism among marine invertebrates 

 has been greatly neglected and this section 

 therefore forms an important contribution to 

 the subject. Incidentally, a detailed account 

 of the myzostomes, almost exclusively parasitic 

 on the crinoids, is given, together with a com- 

 plete list of all the known species. No other 

 list exists at present. 



The coloring of the comatulids, remarkable 

 for its brilliancy and diversity, is treated in 

 detail for the first time, the color of 160 species, 

 in many cases from the author's own notes 

 taken at sea, being given. The pigment is 

 described and the chemical composition of the 

 skeleton is discussed. 



Such, in bare outline, are the contents of an 

 extraordinarily well conceived and thoroughly 

 executed treatise, upon the publication of 

 which the author as well as the authorities of 

 the National Museum. are to be congratulated, 

 for the work will always remain a point of 

 departure for future investigation. 



The press-work of this volume is excellent 

 and an improvement over that of Part 1. The 

 half-rag paper is also a decided advance, al- 

 though really too thin to carry the larger text 

 figures, since the pi'inting on the reverse shows 

 through. A few copies of such fundamental 

 memoirs as the present should be printed upon 

 heavy, full-rag paper, or better stiU upon linen, 

 and deposited in, say, half a dozen "strategic" 

 libraries of the world. Too manv of oiu- basic 



