EVOLUTION AND THEISM. 405 



organization, this aggregate shapes itself into a gastriila or primi- 

 tive stomach— the common possession, at this stage, of all animals 

 that rise above the protozoic condition, which is permanently 

 represented in the Zoophyte. It is iu a certain spot of the wall 

 of this gastrula, that the foundation is laid, in all vertebrate em- 

 bryos, of that which is to become the brain and spinal cord, with 

 its bony investment ; and this " primitive trace " of what is to 

 constitute the essential part of the human organism, does not 

 differ in any essential particular from that of a fish, a frog, a bird, 

 or any ordinary Mammal. So, the early development of the circu- 

 lating and respiratory apparatuses proceeds upon a plan common 

 to all Vertebrates ; even the early Human embryo possessing the 

 gill-arches which are to sprout into gills in fishes and amphibia, 

 though they afterwards disappear in Man (as in reptiles, birds, and 

 mammals) with the development of the lungs and the diversion of 

 the blood-circulation into them. When, in the progress of de- 

 velopment, the distinctively Mammalian type comes to present itself, 

 there is still nothing distinctive of Man ; in fact, the general con- 

 figuration of the body is shaped out, and most of the principal 

 organs have shown their characteristic structure, before the embryo 

 presents any feature by which it could be certainly distinguished as 

 human. And I may specially notice the fact that the cerebru7n, 

 whose great size and complexity of structure constitute man's most 

 important differential character, is evolved as a sort of offset from 

 the chain of sense-ganglia, which is the real basis of the brain in 

 all vertebrates, and continues to represent it in insects ; that it at 

 first presents the small relative size and simple organization which 

 we find permanently retained in the kangaroo or rabbit ; that, as 

 embryonic life advances, it comes more to resemble the brain of a 

 dog or cat, and then that of a monkey — the distinctly Human type 

 manifesting itself last. This is marked, not only in the backward 

 as well as forward extension of the cerebral hemispheres, but in the 

 number and depth of the convolutions which extend the surface of 

 their outer ganglionic layer, and bring it into closer relation with 

 the capillary blood-vessels, on whose supply of oxygenated blood 

 its whole subsequent activity is dependent. 



Now, I cannot suppose any one of you to be ignorant of the 

 fact, that the Human infant at its entrance into the world is de facto 



