342 Bibliographical Notices. 



before. As a result, we have for the first time a real insight into 

 the inter-relationships of this most difficult group. 



The calycinal system is no longer the governing factor in our 

 reckoning of the morphological level of the Echinoderma, as in the 

 systems of Loven, Carpenter, and Sladen. The plates taking part 

 in the apical system of the Echinoidea and Stelleroidea cannot, 

 Mr. Bather shows, now be regarded as merely homogenetic with 

 those of the Crinoidea. The evidence of the fossils is fatal to this 

 conclusion, inasmuch as the Eleutherozoa " if they arose from 

 stalked forms at all, indubitably did so ages before the calycinal 

 system had been evolved." 



The most primitive Echinoderms which we know at present 

 appear to be the Cystidea Amphoridea. From this stock probably 

 branched the Cystidea Rhombifera, Cystidea Diploporita, Blastoidea, 

 and Crinoidea on the one hand, and the Edrioasteroidea and Eleu- 

 therozoa on the other, these last being derivable possibly from the 

 Edrioasteroidea. 



The account of the larval forms, which is absolutely indispensable, 

 is lucidly, if briefly, sketched. Herein the complex coilings of the gut, 

 the changes in the development of the coelom, following the changes 

 from a free-moving to a fixed habit, and the gradual evolution into 

 the characteristic radial symmetry are made as clear as such a 

 difficult matter can possibly be made. Most of the figures 

 illustrating this section are new. That showing the change from 

 the Peutactea to the Eleutherozoic Stelleroid type is very in- 

 structive. 



Mr. Bather supports the view held by many that the simplicity 

 of structure of the Synaptidas is a secondary feature, and that 

 therefore this form cannot be regarded as the simplest and most 

 ancestral of the Echinoderms. The class he regards as a probable 

 early offshoot from the Edrioasteroidea. 



Mr. E. S. Goodrich's summary of the Holothuroidea is admirable 

 and well illustrated. We venture to think he missed an opportunity 

 in not directing attention to the fact that Ludwig's classification 

 does not agree with his phylogenetic tree ; and that whilst the latter 

 may be taken as a more or less probable expression of the relation- 

 ships of the forms included, one to another, the former is artificial, 

 and savours rather too much of a " Key." 



Dr. Gregory has certainly sustained the high standard which 

 characterizes this work. He insists on the close relationship of the 

 Stelleroidea and Ophiuroidea, wherein most will agree with him. 

 It is incorrect, however, to state that Ophioteresis agrees with the 

 Stelleroidea in having an ambulacral furrow. This is an important 

 point, for Dr. Gregory uses it as an instance showing the unreli- 

 ability of this character as a taxonomic factor for the division of the 

 Ophiuroidea from the Stelleroidea. Again, the supposed pore-plates 

 of Botliriocidaris are really tubercles. But these are to be regarded 

 as slips which will creep into every work in spite of the most zealous 

 precautions. 



Prof. Lankester's choice of authors for this work has been in 



