THE DEVELOPMENT OF THE ORGANS. 191 



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." Hid. 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 

 46 



