960 



SCIENCE. 



[N. S. Vol. XII. No. 312. 



distension and fusion of spaces primarily be- 

 longing to the vascular system, a method of 

 ccelom-formation to which Lankester applies 

 the somewhat cacophonic term phlebcedesis. As 

 a corollary of this view of the ccelom a division 

 into two groups of the organs usually termed 

 nephridia has resulted ; those which terminate 

 in a flame cell, such as those characteristic of 

 the Platyhelminths, Rotifers, Chaetopods and 

 of certain larval Mollusca, have been placed in 

 one group and retain the original name, while 

 those which stand in relation with the gono- 

 ccel or its derivatives, such as those of the 

 adult Molluscs, the Arthropods and Verte- 

 brates, form the second group and are termed 

 uroducts. In passing it may be remarked that 

 we cannot help wondering why, in speaking of 

 nephroblasts on p. 34, the credit for their dis- 

 covery is assigned chiefly to Bergh, the actual 

 discoverers, Whitman and Wilson, being prob- 

 ably included in the term ' other observers.' 

 Is it possible that Professor Lankester flnds his 

 greatest joy in one sinner who repents? 



The theory thus briefly outlined has cer- 

 tainly much in its favor, though it must be 

 confessed that doubts are still permissible as to 

 the fundamental distinction between the two 

 forms of coelom. Final judgment on this point 

 must at all events be postponed until further 

 information as to the developmental history of 

 the ccelomic and vascular spaces of such forms 

 as the Nemerteans and Hirudinea is at our dis- 

 posal. 



In connection with the theory Lankester in- 

 troduces many new terms, a list of which with 

 definitions forms the concluding section of the 

 chapter. The majority of these are undoubtedly 

 necessary, if the theory be correct, but the 

 terms Enterocoela and Ccelomoccela, used in the 

 heading of the chapter, and proposed as sub- 

 stitutes for the more familiar names Coelentera 

 and Coelomata, are certainly open to objection. 

 Perhaps they are more symmetrical than the 

 older terms, but a name, after all, is but a peg 

 whei-eon to hang an idea, and a superabundance 

 of pegs for one idea is just as confusing as a 

 lack of one, and, furthermore, the term Entero- 

 coelia has already been employed by the Hert- 

 wigs for the suspension of a very different idea. 



Professor Minchin's chapter on the Porifera 



is admirable in every respect and fully harmo- 

 nizes with the excellent work he has previously 

 published upon the group. His treatment of 

 all the points of view is full and accurate, and 

 his discussion of the affinities of the group and 

 the phylogeny of its various subdivisions is clear 

 and suggestive. He inclines to the view of an 

 early separation of the sponges, as the Parazoa, 

 from the remaining Metazoa and maintains the 

 non-identity of the germ layers in the two 

 groups. The chapter, in a word, may be taken 

 as an accurate and comprehensive statement of 

 our present knowledge of this interesting group. 

 Unfortunately, so much cannot be said with- 

 out reservation regarding the remaining chap- 

 ters of the volume. Mr. Fowler's chapters do 

 not evidence the same familiarity with the forma 

 described that is seen in Professor Minchin's 

 work, and the same is true, to a certain extent 

 at least, of Mr. Bourne's contribution. The 

 chapters on the Hydromedusse and Scyphome- 

 dusse are sketchy, as may be appreciated from 

 the fact that the latter group requires but six- 

 teen pages, or really, if the space occupied by 

 the fourteen figures be deducted, but little 

 more than ten pages. The principal facts con- 

 cerning the structure and histology of the two 

 groups are given, it is true, but the brevity of 

 stj'le which the author affects leads occasion- 

 ally to statements which convey erroneous im- 

 pressions, as, for instance, where it is stated 

 that the threads of the nematocysts ' are formed 

 (sic) and lie inside the vesicles,' where delami- 

 nation alone is given as the method by which the 

 germ layers are formed in the Hydromedusse, 

 and where invagination is alone given as the 

 corresponding process in Scyphomedusse. And 

 one misses also some treatment of the broader 

 questions suggested by the structural peculiari- 

 ties of the group. Thus one finds no discussion 

 of the interesting question as to the origin of 

 the alternation of generations in the Hydrome- 

 dusse, so admirably treated by Brooks, nor of 

 the corresponding phenomenon in the Scypho- 

 medusse, and one searches in vain for any dis- 

 cussion of the phylogeny of the various orders 

 into which the two classes are divided, or for 

 any adequate treatment of the principles under- 

 lying the polymorphism so strikingly mani- 

 fested by the Siphonophores. 



