136 THE PLACOID BRAIN. 



mammalia follow, — each species in due order, according to ita 

 modicum of intelligence ; the birds succeed the mammalia : 

 the reptiles succeed the birds ; the fishes succeed the reptiles ; 

 next in the long procession come the invertebrate animals; 

 and these, too, take rank, if not according to their develop- 

 ment of brain proper, at least according to their development 

 of the substance of brain. The occipital nervous ganglion 

 of the scorpion greatly exceeds in size that of the earthworm ; 

 and the occipital nervous ring of the lobster, that of the in- 

 testinal ascaris. At length, when we reach the lowest or 

 acrite division of the animal kingdom, the substance of brain 

 altogether disappears. It has been calculated by naturalists, 

 that in the vertebrata, the brain in the class of fishes bears 

 an average proportion to the spinal cord of about two to one ; 

 in the class of reptiles, of about two and a half to one ; in 

 the class of birds, of about three to one ; in the class of mam- 

 mals, of about four to one ; and in the high-placed, sceptre- 

 bearing human family, a proportion of not less than twenty- 

 three to one. It is palpably according to development of 

 brain, not development of bone, that we are to determine 

 points of precedence among the animals, — a fact of which no 

 one can be more thoroughly aware than the author of the 

 " Yestiges" himself Of this let me adduce a striking in- 

 stance, of which I shall make further use anon. 



" All life," says Oken, " is from the sea ; none from the 

 continent, Man also is a child of the warm and shallow 

 parts of the sea in the neighbourhood of the land." Such 

 also was the hypothesis of Lamarck and Maillet. In follow- 

 ing up the view of his masters, the author of the " Yestiges" 

 fixes on the Delphinidce as the sea-inhabiting progenitors of 

 the simial family, and, through the simial family, of man. 

 For that highest order of the mammalia to which the Simi- 

 adce (monkeys) belong, " there remains," he says, " a basis 

 in the Delphinidce^ the last and smallest of the cetacean tribes. 



