THE DEVELOPMENT OF THE ORGANS. I9I 



and the lower Apes, than the hand or the foot, and yet, perhaps, there is one 

 organ which enforces the same conclusion in a still more striking manner — 

 and that is the brain."— Man's Place in Nature, p. 94 (1863). 



"As if to demonstrate, by a striking example, the impossibility of 

 erecting any cerebral barrier between Man and the Apes, Nature has 

 provided us, in the latter animals, with an almost complete series of gra- 

 dations, from brains little higher than that of a Rodent to brains little lower 

 than that of Man." — Ibid. p. 96. 



Our investigations, up to the present, have shown us how 

 the whole human body has developed from an entirely simple 

 beginning, from a single simple cell. The whole human 

 race, as well as the individual man, owes its origin to a 

 simple cell. The one-celled parent-form of the former is, even 

 yet, reproduced in the one-celled germ-form of the latter. 

 In conclusion, we must glance at the evolutionary history of 

 the separate parts which constitute the human body. In 

 this matter, I must, of course, restrict myself to the most 

 general and important outlines ; for a detailed study of the 

 evolutionary history of the separate organs and tissues 

 would occupy too much space, and would demand a greater 

 extent of anatomical knowledge than the generality of my 

 readers are likely to possess. In considering the develop- 

 ment of the organs, and of their functions, we will retain the 

 method previously employed, except that we will consider 

 the germ-history and the tribal history of the various parts 

 of the body in common. In the history of the evolution of 

 the human body as a whole we have found that Phylogeny 

 everywhere serves to throw light on the obscure course of 

 Ontogeny, and that the clew afforded by phylogenetic con- 

 tinuity alone enables us to find our way through the labyrinth 

 of ontogenetic facts. We shall experience exactly the same 

 fact in the history of the development of the separate 



