OSTEOLOGY 151 



looked upon as the homologues of the maxillo-palatines of 

 Pliaetlion. But in Fregata both structures are present. 

 Coexistence clearly disproves homology ; we must, therefore, 

 place the ' desmognathism ' of Phalacrocorax upon an 

 entirely different footing from that of the Anseres, where 

 the maxillo-palatines unite in the typical fashion across the 

 middle line. 



In addition to these forms of desmognathism it appears 

 to me that we should distinguish that of the American vul- 

 tures, where there is no union at all of the maxillo-palatines, 

 but only of the alinasals. 



In fact there appear to be three ways of bridging over the 

 palate which may be termed desmognathism, though the 

 word becomes merely descriptive of a condition and not 

 necessarily indicative of affinities ; these are 



(1) Union of maxillo-palatines (more or less complete). 



(2) Union of alinasals. 



(3) Union of maxillae in front of the maxillo-palatines. 

 These three are usually combined in various ways ; e.g. 

 In hornbills there are all three methods of union ; in 



some Steganopodes only numbers 2 and 3. 



Brain and Nervous System. 



The brain of recent birds chiefly differs from that of 

 reptiles by the large size of the hemispheres, the large size 

 of the cerebellum, and by the fact that, owing to the great 

 development of these two regions, the optic lobes are pushed 

 to one side. T. J. PARKEE found in studying the develop- 

 ment of Apteryx that the latter feature is acquired during 

 development, and that the optic lobes have originally the 

 reptilian position. The extinct cretaceous birds had brains 

 with smaller cerebral hemispheres and with larger optic lobes 

 than existing birds, and were in these particulars more repti- 

 lian. On the other hand, if the cast present in the London 

 example of the Arcliceopteryx be really, as it was first surmised 

 to be by Sir JOHN EVANS, the brain of the bird, it was less 

 reptilian than Hesperornis, a fact which may possibly 



