CHAPTER III. 



OP GROWTH IN THE ANIMAL KINGDOM. 



JWnEN molecularly the male fecundating substance has blended 

 with that of the female ovulum (Fig. 40), has impregnated it, the 

 work of evolution, that ia to say, of generation and multiplication of 

 the anatomical elements, has commenced 



in that ovulum. Growth commences 



*in the ovulum by the inferior process 

 of segmentation or fractionment (Fig. 



'41). Cells, all like each other, juxta- 



jpose themselves to form a membrane, 

 in a point of which appears the rudi- 

 ment of the embryon. The primitive 

 membrane is the blastoderm; the first 



Vindication of the embryon is called Anovum 

 the embryonary spot. In this point the g^ S?3ft 



iblastodermic membrane is double; it ^T^ffS^ 



sm, y 

 jping 

 in the 



I is composed of an external vestment, 8tance or protoplasm, yolk of 



7 ovum ; d, enveloping mem- 



serous or animal ; and of an internal brane of * he y* ] n * he mam ~ 



mifers : it is called Membrana 



Vestment. muCOUS Or vegetative. From pellucicla, on account of its trans- 

 parency. 



the first vestment specially proceed, 



in the vertebrates, the teguments and the organs of the life 



of relation ; the second vestment gives, above all, birth to the 

 , apparatus of vegetative life. These first phenomena of develop- 

 iment are perceptibly the same in the whole animal kingdom, 



from the lowest point to the highest. 



