1888.] 



On the Vertebral Chain of Birds. 



475 



" The spines connected with the neuroids ought to be called, as 

 before, neural spines; those connected with the pleuroids, pleural 

 spines. 



"The real centrum of the vertebra ought to be called centrum; 

 the lateral elements composing it hemicentra (Albrecht), not pleuro- 

 centra. 



"The name inter centrum ought to be preserved. 



" The part of the inter centrum, centrum, or neuroid to which the 

 capitulum is articulated, may retain the name parapophysis ; the part 

 of the centrum or neuroid to which the tuberculum is articulated may 

 retain the name diapophysis." 



If we consider the structure of a bird as compared with a Reptile 

 or a long- tailed Mammal, it would seem to have no necessity for the 

 development of " chevron -bones " or inter centra. ; yet these elements 

 are constantly present at the two extremities uf the vertebral chain, 

 although in the hind-part they are often not more developed than 

 those seen in the lumbar region of the Mole (Talpa europcea). 



If all birds have come up to us through forms similar to the 

 Archceopteryx, then there must have been a slow, secular degradation 

 of these inferior arches: that view, however, places the Toothed 

 Birds of the Cretaceous Period as far from those Saururous types as 

 the Birds of the present time. 



That the aquatic, gill-bearing forms from which, originally, the 

 Reptile and the Bird both arose were long-tailed, I have not the least 

 doubt. One thing, however, I never can see, and that is that there 

 was any absolute necessity that there should be just one pair of those 

 old quasi-larval Dipnoans (or Amphibians) that had, at that im- 

 measurably remote epoch, "the promise and potency" of all those 

 Reptiles and Birds that we know have arisen, and of all those myriads 

 of others of which we know nothing. 



As the times became ripe for the harvest of scaly and feathered 

 .'orms, they did appear, but had they all one father and .one 

 mother ? 



Another question to be asked is, Were there ever any per saltum 

 rises in the scale; did all those nobler and still nobler forms acquire 

 their varying degrees of excellency, from a low Reptile to a high 

 Singing-bird, by the slow accretion of growth, and almost imperceptible 

 change of structure, and increase of faculty ? 



It would greatly relieve my mind if it could be shown that the 

 most probable hypothesis is that the swarm of old Perennibranchiates 

 in a thousand places, and at varying times, changed for the better ; 

 became sometimes rapidly, at other times more slowly, transformed 

 as the occasions arose ; when the dilemma was transform or die. 

 That is the dilemma, now, to all our native Amphibia year by 

 year, and that which takes place now in forms that rapidly rise to 



