Prof. W. K. Parker. 



[Jan. 27, 



If many of the existing Yertebrata are metamorphic now, is it not 

 very probable that they were all metamorphic once ? 



The fact that we have, even now, such forms as the larval lamprey 

 (or Ammoccete), the larv83 of Ganoids and Dipnoi, and the tadpoles 

 of newts and frogs, suggests to me the possibility of the existence of 

 hnge swarms of low Proto -Yertebrata in the early ages of the inhabited 

 planet. 



If such proto-vertebrate forms existed, then it is quite supposable 

 that a metamorphosis may, from time to time, have taken place, of 

 this and that quasi-larval form into archaic reptile, ancestral bird, or 

 primitive mammal. 



I am not afraid that anyone familiar with the development, 

 structure, and habits of the existing Amphibia will see any difficulty 

 in the passage of a metamorphic into a so-called non-metamorphic 

 type, during time, and under the pressure of new outward conditions, 

 — when the dilemma offered to the supposed low vertebrate was 

 Transform or perish. 



To me it seems that the creature's necessity was Nature's oppor- 

 tunity ; and that, during long ages, the morphological force had 

 accumulated in those low forms an enormous surplusage of unused 

 energy which, in the ripeness of time, blossomed out into this and 

 that new and noble type. 



Of all the types of Yertebrata, there is none like the bird of high 

 degree for illustrating what Professor Huxley calls "the threefold 

 law of evolution,"* namely, overgrowth of some parts, starvation and 

 even death of others, and fusion of parts originally distinct. 



No kind of vertebrate whatever presents to the osteologist so hope- 

 less an enigma in the adult skeleton as that of the bird; in the 

 overgrowth of certain parts, the abortion or suppresion of others, 

 and the extensive fusion of large tracts of skeletal elements. 



Hence this Class has largely acted upon the morphological mind ; 

 the " Comparative Anatomist " has, of necessity, undergone evolution 

 into the " Morphologist," and the latter has had to be refined and 

 developed into the " Embryologist." 



In the bird class we meet with this remarkable phenomenon, 

 namely, that the swiftest creatures by far that inhabit the earth have 

 had, for the purposes of their most consummate mechanism, the 

 greatest loss of freedom of the individual parts of the skeletal frame- 

 work. 



Between the pigeon, on one hand, above, and the emeu, on the 

 other, below, there are several families of related birds ; but there is 

 no direct superposition,— they are obliquely above or below each other. 



* See his paper " On the Application of the Laws of Evolution to the Arrange- 

 ment of the Vertebrata, and more especially of the Mammalia" (' Zool. Soc. Proc.,' 

 December 14, 1884, pp. 649-662). 



