Bibliographical Notices. 365 



opportunity of indicating the morphological relations of his classes, 

 which may be traced with gradually increasing clearness in the three 

 higher divisions, whilst the only advantage gained by it is that he 

 gets over the difficulty of determining whether the Echinodermata 

 should be placed in one or other of two sections. 



Professor Van der Hoeven excludes the Sponges altogether from 

 the Animal Kingdom, — a course which has been adopted by some 

 other continental zoologists, with but little justice, as it appears to 

 us : his classification accordingly commences with the Infusoria, 

 which may be regarded (with the above exception) as equivalent 

 to the Protozoa, including both the true Infusoria and the Rhizo- 

 poda ; and, singularly enough, considering that the Sponges are ex- 

 cluded, the Volvocina are still placed among the former, as are also 

 some other forms {Vibrionidce) whose vegetable nature is generally 

 regarded as fully established. 



The Radiata of modern authors form the three following classes, 

 the Polypi, Acalephce, and Echinodermata. Amongst the Polyps, 

 Professor Van der Hoeven still includes, not only the Hydroida, but 

 also the Bryozoa, although he admits that the latter would almost 

 be better placed with the Mollusca. Of course, as the Hydroid 

 Polyps are grouped in the same class with the true Polyps, the class 

 of Hydrozoa of modern authors (the Hydras-medusae of Leuckart) 

 is not recognized by our author ; his class of Acalephae includes 

 exactly the same elements as that of Cuvier, — a circumstance which 

 is to be regretted, as the curious relations of the Hydrozoa, and the 

 remarkable phenomena of their so-called alternation of generations 

 can only be satisfactorily understood by regarding the Hydroid Po- 

 lyps and Acalephee as forming a single great group. The Sipuncu- 

 tacea are included amongst the Echinodermata. 



With the fifth class, that of the Entozoa, divided into the two 

 orders Sterelmintha and Ccelelmintha, we commence the great series 

 of theAnnulosa, including the classes Rotatoria f Annulata, or Ringed 

 worms, of which the Turbellaria constitute the first order, Insecta 

 (with the Myriapoda), Arachnoidea, and Crustacea. 



The Mollusca, with our author, form three great classes, the 

 Tunicata, the Conchifera, and the Mollusca. Considering the vast 

 differences of organization existing between the Brachiopoda and 

 Lamellibranchiata and the Gasteropoda and Cephalopoda, we cannot 

 regard this arrangement as at all satisfactory on any grounds, and 

 should have greatly preferred seeing the Mollusca divided, in ac- 

 cordance with ordinary usage, into at least five classes (besides the 

 Bryozoa). 



The Vertebrate Animals, which of themselves occupy the whole of 

 the second volume, are divided into four classes, the author not re- 

 garding the distinctions manifested between the Batrachia and the 

 true Reptiles as sufficient to warrant their separation into two classes. 

 The classification adopted for the Fishes is to a certain extent modi- 

 fied in accordance with the views of Professor Miiller, — that is to 

 say, the Leptocardii and Cyclostomi are regarded as forming a distinct 

 section from the Chondropterygii (Selachii of Miiller), and the 



Ann. $ Mag. N. Hist. Ser. 3. Vol.il 25 



