1887.] 



On the Morphology of Birds. 



53 



The bibliography of my published papers on the Osteology of the 

 Thorax partly, and of the Skull largely, is given in the general 

 Bibliographical List. It has been necessary to do this, as every scrap 

 and part of the older work is wanted, now that an attempt is made 

 to build the old and the new into something like a structure having 

 form and fulness. 



There are several things that go to increase the interest in the 

 morphology of these culminating Sauropsida at the present time. 



First. — The discovery by Gegenbaur, Huxley, and others, of the 

 close relationship of birds and reptiles, especially of the extraordinary 

 fact that the hind limb and pelvis of even the most minute bird pass 

 through a stage in which they correspond almost exactly with the 

 hind limb and pelvis of the most gigantic kinds of extinct reptiles — 

 the Dinosaurs or Ornithoscelida. 



Secondly. — The recent discoveries of biologists as to the composition 

 of the Cheiropterygium in the various types of air-breathing Verte- 

 brata. It is now well known that the five-fingered hand and the foot 

 with five toes are the specialised modern representatives of hands and 

 feet that had at least seven rays in their composition. 



And, thirdly — the study of the development and general morphology 

 of birds is, at the present time, of great interest, — now that we are 

 looking to the study of metamorphosis for some initial elucidation of 

 the mystery as to the origin of the various types of Yertebrata. 



The labour of each succeeding day at this culminating Class makes 

 it more and more impossible for me to conceive of birds as arising 

 direct from the Dinosaurians, or indeed from any other order or 

 group of reptiles. 



Long attention to the metamorphosis of the Amphibia has intensified 

 this difficulty to me ; for the newly- transformed frog or newt appears 

 to me to be the true counterpart of a newly-hatched reptile — snake, 

 lizard, turtle, or crocodile. 



Each of these young creatures, whether it has undergone a true 

 metamorphosis, or has been the subject of pre-natal transformation, is 

 evidently an imago ; although an imago that continues to grow. 



Now each amphibian has its own larva, for the larvae of the various 

 species have their specific differences. 



The thousand known species of existing Amphibia — Anurans, 

 Urodeles, and Coecilians — and all the fishes that undergo metamor- 

 phosis, are as truly, if not as remarkably, distinct from each other in 

 their larval as in their imago form ; — as much so as is the case in 

 insects, or any other of those invertebrate types that are truly meta- 

 morphic. 



materials for this and other parts of my work, I cannot reproduce it here ; but must 

 use this opportunity of thanking a host of kind friends for gifts which, in abundance 

 and variety, are somewhat embarrassing. 



