THE VEGETABLE AND ANIMAL, KINGDOMS. 103 



fory, through a series of changes resembling th( permanent 

 forms of the various orders of animals inferior to it in the 

 scale. Thus, for instance, an insect, standing at the head 

 of the articulated animals, is, in the larva state, a true 

 annelid, or worm, the annelida being the lowest in the 

 same class. The embyro of a crab resembles the perfect 

 tnimal of the inferior order myriapoda, and passes through 

 all the forms of transition which characterize the interme- 

 diate tribes of Crustacea. The frog, 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 ad- 

 vances to maturity, and becomes a land animal. The 

 mammifer only passes through still more stages, accord- 

 ing to its higher place in the scale. Nor is man himself 

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

 permanent in the animalcule. His organization gradually 

 passes through conditions generally resembling 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 cha- 

 racteristic 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 see, 

 the varieties of his race are represented in the progressive 

 development of an individual 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, w 7 hich exceeds that of all other animals in 

 complexity of organization, and fulness of development, 

 is, at one early period, only " a simple fold of nervous mat- 

 ter, with difficulty distinguishable into three parts, while 

 a little tail-like prolongation towards the hinder parts, and 

 which had been the first to appear, is the only represen- 

 tation of a spinal marrow. Now, in this state it perfect- 

 ly 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, the spinal marrow better marked ; 

 it is now the brain of a reptile. The change continues ; 

 by a singular motion, certain 'parts, {corpora quadrage- 

 mina) which had hitherto appeared on the upper surface 

 now pass towards the lower ; the former is their perma- 

 nent situation in fishes and reptiles, the latter in birds 



