EMBRYONIC INVESTIGATIONS. 163 



pendeuce of action can be sustained, and development pro- 

 ceeds, aided by the actions going on simultaneously in the 

 surrounding cells, producing changes on them, and having 

 changes produced in them in turn on themselves. The existence 

 of and discharge of ova during childhood, and the incomplete- 

 ness of the organization of such ova, by which impregnation 

 is rendered impossible ; the existence of the nuclei, which 

 suffer less change, or resist changes longer than the cell; 

 the formative power which the cells of the ovary appear to 

 possess even after the extension of the ova, as witnessed in 

 the corpus lecteum ; the numbers of ova beyond all seeming 

 needs ; the appearance of the germinal vesicle first in the order 

 of development, and the analogy between the sperm and the 

 germ in their development, are all suggestive of this view. 



In the preparations for fecundation the mother-cell of the 

 estes possesses nuclei which develop into spermatozoa and 

 are scattered as animated particles within the secretions 

 of the seminal tubes. In the ovum, as a preparation for 

 fecundation, it seems probable from the observations of many 

 skilled observers, that the germinal vesicle is dissolved (like 

 the mother-cell), and the diffusion of its contents (which 

 originate or are formed from the germinal spot or nucleus) 

 through the yolk, which may be considered in some sense a 

 secretion. 



Certain it is that the ovum, like the spermatozoon, repre- 

 sents vitality. A period in its development arrives when it 

 becomes capable, under fit conditions, of establishing an indi- 

 vidual and independent life. This condition of vitality may 

 remain for a considerable, though uncertain, period of itself; 

 the ovum has reached the highest development that it is ordi- 

 narily capable of, and it requires for its future development a 

 set of conditions external to itself, the union of the fecundat- 

 ing srerm and fit surroundings. 



This ovum is, however, filled with possibilities. It con- 

 tains, as does the sperm, elements which may go to make up 

 an individual and independent life, and is one of the connect- 

 ing links which unite all the vital forces of the past with 

 future generations. It is a vehicle for the transmissal of the 

 forces which have had part in its own evolution. 



Each cell or completed ovum contains its own forces, which 



