48 APHORISMS AND REFLECTIONS 



existence under a form different from, and simpler 

 than, that which it eventually attains. 



The oak is a more complex thing- than the little 

 rudimentary plant contained in the acorn ; the 

 caterpillar is more complex than the egg ; the 

 butterfly than the caterpillar ; and each of these 

 beings, in passing from its rudimentary to its perfect 

 condition, runs through a series of changes, the sum 

 of which is called its development. In the higher 

 animals these changes are extremely complicated ; 

 but, within the last half century, the labours of such 

 men as Von Baer, Rathke, Reichert, Bischoff, and 

 Remak, have almost completely unravelled them, so 

 that the successive stages of development which are 

 exhibited by a dog, for example, are now as well 

 known to the embryologist as are the steps of the 

 metamorphosis of the silk-worm moth to the school- 

 boy. It will be useful to consider with attention the 

 nature and the order of the stages of canine develop- 

 ment, as an example of the process in the higher 

 animals generally. 



CLXXIII 



Exactly in those respects in which the de- 

 veloping Man differs from the Dog, he resembles 

 the ape, which, like man, has a spheroidal yelk-sac 

 and a discoidal, sometimes partially lobed, placenta. 

 So that it is only quite in the later stages of develop- 

 ment that the young human being presents marked 

 differences from the young ape, while the latter 

 departs as much from the dog in its development, as 

 the man does. 



Startling as the last assertion may appear to be, it 

 is demonstrably true, and it alone appears to me 

 sufficient to place beyond all doubt the structural 

 unity of man with the rest of the animal wrorld, and 

 more particularly and closely with the apes. 



Thus, identical in the physical processes by which 



