THE VEGETABLE AND ANIMAL KINGDOMS. 119 



highly organized fish, exhibits, in its early stages, as has 

 been remarked, the gelatinous dorsal cord, the heterocercal 

 tail, and inferior position of the mouth, which mark the 

 mature example of the cartilaginous fishes. The frog, again, 

 for some time after its birth, is a fish with external gills, and 

 other organs fitting it for an aquatic life, all of which are 

 changed as it advances to maturity and becomes a land 

 animal. The mammifer only passes through still more stages, 

 according to its higher place in the scale. Nor is man him- 

 self exempt from this law. His first form is that which is 

 permanent in the animalcule. His organization gradually 

 passes through conditions generally resembling a worm, a fish, 

 a reptile, a bird, and the lower mammalia, before it attains its 

 specific maturity. At one of the last stages of his foetal 

 career, he exhibits an intermaxillary bone, which is charac- 

 teristic of the perfect ape ; this is suppressed, and he may then 

 be said to take leave of the simial type, and become a true 

 human creature. Even as we shall find, the varieties of his 

 race are represented in the progressive development of an in- 

 dividual of the highest, before we see the adult Caucasian, the 

 highest point yet attained in the animal scale. 



To come to particular points of the organization. The 

 brain of man, which exceeds that of all other animals in com- 

 plexity of organization and fulness of development, is, at one 

 early period, only " a simple fold of nervous matter, with 

 difficulty distinguishable into three parts, while a little tail- 

 like prolongation towards the higher parts, and which had 

 been the first to appear, is the only representation of a spinal 

 marrow. Now, in this state it perfectly resembles the brain 

 of an adult fish, thus assuming in transitu the form that in the 

 fish is permanent. In a short time, however, the structure is 

 become more complex, the parts more distinct, and the spinal 

 marrow better marked ; it is now the brain of a reptile. The 

 change continues ; by a singular motion, certain parts (cor- 

 pora quadrigemind) which had hitherto appeared on the upper 

 surface, now pass towards the lower ; the former is their per- 

 manent situation in fishes and reptiles, the latter in birds and 



