Rerieics — Professor Lanlccster's Zoolocjy. 525 



s, E "x;^ z E AAT s. 



A Treatise on Zoology. Edited by E. Eay Lankester. 

 Part III : The Porifera and Ccelenterata. By E. A. 

 MiNCHiN, M.A., G. Herbert Foavler, B.A., Ph.D., and 

 Gilbert C. Bourne, M.A., with an Introduction by E. Eay 

 Lankester. pp. vi and 368, with 227 figures in the text. 

 (London : Adam & Charles Black, 1900.) 



PEOFESSOPt LANKESTEE is to be congratulated on the speedy 

 appearance of another part of his " Treatise on Zoology," and 

 it is to be devoutly hoped that the remaining eight parts will 

 appear with even greater rapidity if the work is to be completed 

 before the first volumes are out of date. 



The present part is of special interest to students of comparative 

 morphology, since it contains a chapter by the editor on the much 

 vexed subject of the coelom. Speculations concerning the origin 

 and homologies of the variously developed body-cavities found 

 among the Metazoa have so long been associated with Professor 

 Lankester's name that an article giving his latest views on this 

 subject will command careful attention from all, even although 

 some may be of the opinion that the present state of our knowledge 

 concerning these cavities is not sufficient to justify all his con- 

 clusions. As an argument against the too previous introduction 

 of the coelom as a feature of classificatory value, we may compare 

 the use made of it in the present work with that adopted by 

 Sedgwick in his recent textbook : the latter authority would exclude 

 the Platyhelmia, the Nematoidea, the Nemertina, and the Eotifera 

 from his Coelomata, whereas Lankester includes all these in his 

 grade Coelomocoela, a term which he proposes to substitute for the 

 well-known Coelomata. 



With reference to these new terms, of which there are several, 

 we should have thought that Professor Lankester's long experience 

 as a teacher would have shown him the futility and undesirability 

 of overburdening a science with new words, especially when they 

 only serve to replace terms long sanctioned by use, solely on the 

 grounds that his new words are more expressive than the old ones. 

 If we were once to commence to replace all the old morphological 

 terms at present in use which, being invented by our more fanciful 

 forefathers, are now found through our increasing knowledge to be 

 deprived of some of their meaning, we should find ourselves lost, 

 like the modern systematist, in a maze of words, and all solid 

 work would be at a standstill. While we would deplore the mere 

 substitution of terms like Coelomocoela for Coelomata and Enterocrola 

 for Ccelenterata, we find no objection to the invention of terms to 

 express fresh ideas, and it is possible that the term Phleboedesis, 

 as applied to the origin of the body-cavity in the Arthropoda and 

 MoUusca, may be found a very useful one. At any rate. Professor 

 Lankester's exposition of his theory of Phleboedesis is very 

 instructive. 



