344 PKOF. OWEN OH THE SKULL OF MEGALOSATJKUS. 



portant relations and affinities are thereby masked. Although the 

 last two classes (Mammalia and Aves) agree as i hot-blooded 

 Vertebrates ' in their higher cerebral development, and in the more 

 complex heart and lungs, Birds, by their genetic and developmental 

 characters, as well as by the general plan of the organization, are 

 more intimately and naturally allied to the oviparous Saurians than 

 to the viviparous Mammals." 



So, likewise, I proceeded to state that " in their generation and 

 development, modern Batrachians differ from other cold-blooded 

 air-breathers and agree with fishes : both classes are 'an allantoic' and 

 branchiate, whilst Birds and Reptiles are ' allantoic and abran- 

 chiate'"*. 



The occipital condyle offered no available character in this 

 division and association of vertebrate animals. The condyle is 

 single in most fishes as in the abranchiate Ovipara ; and it is convex 

 in some kinds, e. g. the Pipe-fishes (Flstularia) f, as in Birds. 

 On the other hand the occipital condyle is double in the batrachian 

 air-breathing Anailantoids or Branchiates, as it is in Mammals. 



In short, in the preliminary chapter of my ' Anatomy of Verte- 

 brates,' I found no other than the developmental characters above 

 cited to add to those which John Hunter, in the previous century, 

 had defined in his ' Schemes of the Classification of Animals.' 



They are given in the ' Essays and Observations on Natural His- 

 tory,' published with notes in 1861 (two vols. 8vo, Van Voorst, 

 vol. i. p. 28) ; and the subjoined quotation may be acceptable. 



" Of the similarity of many Parts of the Fowl and Three-cavity- 

 hearted Animals " (which Hunter termed Tricoilia ~ Reptiles). 



" The lungs of the fowl open into thin cells or bags that are in the 

 cavity of the belly. The cells of the lungs are large. The lungs in 

 the Tricoilia are continued into the belly, are cellular at the upper 

 part, but in most, e. g. the snake, become smooth bags at the lower 

 end as it were, answering the same purpose as the abdominal bag 

 in fowls : the cells of the lung-part are large. 



" No proper diaphragm in either class, but fowls have something 

 similar to one." (The degree in which it most nearly attains the 

 mammalian character is shown in my " Anatomy of the Apteryx," 

 Zool. Trans, vol. i.) 



" The gall is green in both. The kidneys are placed in what may 

 be called the pelvis in both ; they are conglomerated in a particular 

 manner, have the ureter ramifying through their whole substance, 

 and it enters into the rectum. The urine is a chalky substance 

 in many of both classes, and is a kind of slime in others. 



" The testes are situated in the abdomen in the males of both. 

 The vasa deferentia enter the rectum in both. The penis is grooved 

 in both. Both are oviparous. 



" The structure of the ear is similar " (p. 28). 



To these characters I added the subsequently determined develop- 



* ' Anatomy of Vertebrates,' torn. cit. p. 7. 

 t Tom. cit. p. 7. 



