CHAPTER X. 



THE DEVELOPMENT OF THE CAT. 



1. BY " the development of the cat " is signified the sum of those 

 rapidly succeeding morphological and physiological changes which 

 commence the life history of the animal. They are changes of great 

 importance and significance changes in the very nature of the 

 creature undergoing them, as well as in the forms and relations of 

 the different parts of the body which successively come into existence. 

 Each individual of the species upon attaining majority, naturally 

 develops one or other of those two products which have been described 

 in the eighth chapter ova and spermatozoa. 



"We may consider the formation of these products as the culmina- 

 tion of the individual's development, and we may consider the 

 conjunction of those products as the initiation of another individual's 

 life. The series of changes, then, which make up the cat's life 

 history, is a series which tends (the requisite conditions being 

 supplied) to return in a cycle. The impregnated ovum becomes, as 

 we shall see, an embryo ; the embryo, a foetus ; the foetus, a kitten ; 

 and the kitten, a cat, destined to give rise to, or to fertilize, another 

 ovum like that with which this cycle of changes began. By the 

 cat's "development," then, should be meant the entire sum of 

 changes it undergoes, from its condition as an impregnated ovum 

 till maturity ; but practically it has come to mean (as above said) 

 that early part of the process which takes place up to, and till 

 shortly after, birth. Thenceforward the changes which ensue are 

 less changes in the forms and relations, than in the dimensions of 

 parts ; and the process of " development " becomes mainly a process 

 of " growth." 



2. But the ovum undergoes certain initial changes, even before 

 impregnation takes place, which changes may nevertheless be re- 

 garded as a part of the developmental process. Such changes, how- 

 ever, as well as some others (especially those of the earliest stages of 

 development after impregnation), have not been actually witnessed in 

 the cat's ovum. Nevertheless, the analogies of animals generally, on 

 the one hand, and of animals nearly allied to the cat on the other, 

 make it possible to infer what those changes in all probability are. 



The ovum having attained to the condition already described in 



