CHAPTER XXXT 



PROTECTION 

 OF YOUNG 



The cat takes care of its 

 kitten. 



The young kangaroo in its 

 mother's pouch. 



What proportion of offspring lives to maturity f What is the relation 

 of the period of adolescence to length of life? Do all animals take 

 care of their young f What animals show the greatest parental in- 

 stinct f 



We have already learned that all plants and animals start life as 

 single cells. In some species this single cell is a spore, in others 

 a zygospore, and in still others a fertile egg. Whether the crea- 

 tm-e is a Paramecium or an elephant, it started life as a single cell. 



The offspring of simple organisms. AVhen an amoeba, a bac- 

 terium, or any other one-celled organism divides into two new 

 cells, the production of the new individuals marks the disap- 

 pearance of the parent. It is impossible for the daughter cell and 

 the mother cell to exist at the same time. Yet, it would not be true 

 to say that the mother cell dies, for the protoplasm of which it 

 consisted continues to live in the two new daughter cells. Each 

 of the young amoebas is quite as capable of taking care of itself 

 as is the older individual from which each came. Except for the 

 growth in the comparatively short time between one cell division 

 and the next, which in the case of some organisms would be only 

 about twenty minutes, the young individual is in every way like 

 the full-growm individual. There is, probably, some difference in 

 size, however. 



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