478 



Prof. W. K. Parker. 



[Mar. 22, 



two crura, and these may meet below and form a Jicemal canal ; in the 

 Cormorant they are solid, and are manifestly developed for steering 

 purposes — as in the Kestrel or Windhover (Falco tinnunculus) . The 

 habits of that voracious, rapid, and powerful bird (the Cormorant) 

 explain the teleology of these strong arid solid intercentra of the tail. 



Coming now to the ribs, my two chosen types, the Swan and the 

 Cormorant, will be the best instances to show how thin the partition 

 is between a hot-blooded bird, and a cold-blooded generalised Reptile, 

 like the Crocodile. In my earlier papers on the Osteology of Birds, I 

 wrote in a general and somewhat confused manner about reptilian 

 characters in Birds ; but Professor Huxley's inestimable paper " On 

 the Classification of Birds " (* Zool. Soc. Proc.,' 1867, pp. 415— 

 472), so thoroughly ventilated the relations of the two great classes, 

 Reptiles and Birds, showing indeed that in a very true sense the two 

 were one, a huge double class — base below and noble above — that if 

 I am confused now, it is not the fault of my " guide." 



It is perfectly true that the Ratitae, on the whole, are the lowest, 

 most generalised, and most reptilian of birds ; but they have a high 

 degree of ornithic specialisation in some parts, much beyond what is 

 seen in some other birds that, on the whole, belong to a much higher 

 level. 



Now the Ratitae are related to a large number of families of birds, 

 that like themselves have cylindroidal vertebrae up to the sacrum ; and 

 there is an almost natural and complete series of these forms, Tinamous, 

 Hemipods, Fowls, &c, &c. But as I showed many years ago, the 

 Duck-tribe and the Fowl-tribe have a skull which is fundamentally 

 alike in both groups, and is unlike that of any other kind of bird's 

 skull, and yet is easily derivable from the Struthious type, by this 

 and that gentle metamorphic alteration. 



But if the Cormorant and his relatives were each derived from 

 Ratitae, they must have been quite unlike those now existing ; a Swan, 

 strange as the assertion may sound, is modified from an essentially 

 Struthious embryo. I have traced it step by step. 



But the Cormorant, and the Darter (Plotus), its nearest relative, 

 seem more like a survival of transformed Plesiosaurs, and their Verte- 

 bral Chain is so intensely Reptilian that, among living forms, the 

 Crocodile is the best guide to the morphologist in its interpretation. 



On the Bibs of Birds. 



I will first describe the ribs of the Swan, and then those of the 

 Cormorant. 



In Gygnus olor, as in all the normal " Chenomorphae," the vertebral 

 artery, right and left, runs inside a series of bridges, which, eked out 

 by strong membrane, form a canal all along the neck. The piers of 

 these small bridges are formed by the upper and lower transverse 



