peters' handbook of zoology. 39 



Tliis circumstance may be of little consequence to the advanced 

 student, who forms his own conclusions upon classification, and 

 views such books as this by the light of an intelligent criticism, but 

 to the beginner it must be not a little puzzling to find that groups 

 treated apparently as equivalent are really of very different value, 

 and that what is spoken of as a class in one page is subsequently 

 divided into classes. Thus the Arthropoda and Vermes which stand 

 as primary heads in this book, are regarded by Dr. Cams as sections 

 of the Annulosa, to which great division of the animal kingdom he 

 likewise refers the third main section (Echinodermata) ; and both 

 the Vermes and Echinodermata are mentioned as classes (pp. 422 

 and 485) whilst their subdivisions are also described as classes. 

 And again these groups appear as if equivalent to the Coelenterata 

 and Protozoa which follow them, but which are universally allowed 

 to be of higher systematic rank. It may be thought that such 

 remarks savour of hypercriticism, but let any one look back to the 

 period of his first steps in science and he will hardly be inclined to 

 make light of such a iault as want of method in a student's manual. 

 It is to be hoped in the interests of a sound zoological system, that 

 when the first volume of this '* Handbook" makes its appearance a 

 table of classification showing the true relations and subordinations 

 of the groups may form part of its contents. The Echinodermata 

 are divided by Dr. Cams into the usual four orders — viz., Holothu- 

 rioidea, Echinoidea, Asterioidea, and Crinoidea. 



"With regard to the classification of the Coslenterata, which are 

 adopted here as constituting a primary division, our author difters 

 somewhat from the views advocated by Huxley. Eecognizing the 

 two types of structure represented by the Actinozoa and Hydi'ozoa 

 of that distinguished zoologist, he yet divides the Coelenterata into 

 three classes, considering the characters presented by the Ctenophora 

 to be of sufficient value to entitle them to rank as a distinct class. 

 In this he is probably right, as, notwithstanding the unmistakeable 

 resemblance of some of the Ctenophora to such Actinian forms as 

 llyantkus and Fhilomedusa, the bilateral symmetry of the body, the 

 nature of the tentacles when present, the peculiarities of the canal- 

 system, the degree of development of the nervous system, and the 

 ciliated paddles by which the free movements of the animals are 

 eftected, would seem to entitle them to rank as a group apart from 

 the Anthozoa. The latter arc described by Dr. Cams under the 

 name of Polypi, and his classification of them is founded upon that 



