10 



ANIMALS, MINERALS, AND PLANTS 



IK. 



'■'M 



m:,zi 



is like every other animal in one respect ; each begins 

 as one cell and, when mature, is made up of either one cell 



;,.•;....,,■. _-.,. (Fig. 2), or a combination of many 



|;i::;:;^^;/:^;::;i:;:j cells, together with the substances 



;;•;•:! ■;i;.v;:;;;;;;'|:;; Qj lying between, which connect the 



i,^;;-;^-/:;;;;iv-|;-:^ cells and hold them together. For 



[■J?;;::-"::;;';!:' J example, one oi the simplest am- 



mals, the amoeba, is composed of 

 but one cell, during its whole life. 

 If^^ On the other hand, the whale is 



made up of milhons of cells, to- 

 gether with the substances which lie 

 between the cells and hold them in 

 place. The one cell of the amoeba 

 -~n performs all the functions of Ufe, 

 i.e. assimilation, reproduction, res- 

 piration, growth, etc. ; while in the 

 body of the whale, these functions 

 are distributed among groups of 

 cells, each group having its own 

 special function to perform. 



l^Mi^:^ 



V.'.".':.J^H-*^i'."'"- 



■'■'■?'«;■•■;•'■■'■'.«,•' 

 ':.fjF: ■■■'::'. ■'■■■:■■■. 



Fig. 2. — Cell of epithelial 

 tissue; a, cilia; n, nucleus. 



