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SOME NEW BOOKS 



The Backboned Animals 



A Classification of Vertebrata, Recent and Extinct. By Hans Gadow. 8vo, 

 pp. xvii + 82. London : A. & C. Black, 189S. Price, 3s. 6d. net. 



This is a valuable and convenient handbook for the use of students 

 attending lectures on the vertebrate animals. It can also be used as 

 a notebook, being printed on one side of the paper only. 



Dr Gadow defines the Vertebrata as " bilateral symmetrical 

 animals with segmentally arranged mesoderm, with a central solid 

 axis (Chorda dorsalis, extending through the whole length of the 

 body, from head to tail, hence holochonhite), dorsally of which lies the 

 tubular central nervous system, ventrally the gut ; the respiratory 

 organs arise from the anterior portion of the gut." He then proceeds 

 to define the ' sub-phyla ' and smaller divisions with commendable 

 brevity and conciseness. As he remarks, there is no reason to 

 enumerate any but the fundamental characters. " For instance, ' the 

 possession of visceral arches, one pair of which is modified into jaws,' 

 is a quite sufficient diagnosis of the Gnathostomata. The presence of 

 an anterior and a posterior pair of limbs is probably quite as essential 

 and peculiar a feature. There are not, and can never have been, 

 paired-limited vertebrata without visceral-arch jaws ; consequently, 

 wherever the converse is the case, we feel certain that the absence of 

 limbs is a secondarily produced feature." Dr Gadow also lays special 

 stress on skeletal characters, not merely on account of their supreme 

 importance, but also because the vast array of extinct animals can 

 only be treated as skeletons. As he well observes, " we do not know 

 that the Palaeozoic Fishes did possess an entirely venous heart, nor 

 has it yet been shown that the embryos of Dinosaurs were surrounded 

 by an amnion ; but we feel nevertheless certain, because of the laws of 

 correlation which comparative anatomy allows us to deduct from the 

 study of recent creatures. On the other hand, it is quite possible, even 

 most likely, that the Triassic Pseudosuchia had no copulatory organ, 

 and therefore this feature cannot be admitted into the diagnosis of 

 Crocodilia, at least not if they are to comprise the Pseudo-, Para-, and 

 Eusuchia." Finally, the author is to be commended for his selection 

 of generic names. The book is " meant to be used by the present 

 generation," and hence he employs those names under which the whole 

 story of vertebrate anatomy and zoology has been written, ignoring 

 certain recent papers which are rather literary essays than contribu- 

 tions to knowledge. 



Dr Gadow recognises two sub-phyla of Vertebrata, namely the 



