82 MAN AND THE LOWER ANIMALS. n 



application, that ever} 7 living creature commences 

 its 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, Eathke, 

 Eeichert, Bischoff, and Eemak, have almost com- 

 pletely 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 metamor- 

 phosis 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 de- 

 velopment, as an example of the process in the 

 higher animals generally. 



The dog, like all animals, save the very lowest 

 (and further inquiries may not improbably remove 

 the apparent exception), commences its existence 

 as an egg: as a body which is, in every sense, as 

 much an egg as that of a hen, but is devoid of 

 that accumulation of nutritive matter which 

 confers upon the bird's egg its exceptional size and 



