69 



In proportion to the number of generations of germ- cells, 

 with the concomitant dilution of the spermatic force, and 

 in the ratio of the degree and extent of the conversion of 

 these cells into the tissues and organs of the animal is the 

 perfection of the individual, and the diminution of its power 

 of propagating without the reception of fresh spermatic 

 force. 



In the vertebrate animal the whole of this force originally 

 diffused amongst the cells or nuclei of the germ-mass is 

 exhausted in the development of the tissues and organs of 

 the individual, in the mysterious renovation of the spermatic 

 power in the male by a special organ, and in the develop- 

 ment of ova or cells prepared fit for its reception in the 

 female. It now and then happens, even in the highest of 

 Vertebrata the human species that an ovarian germ-cell 

 sets up the process of embryonic development, but without 

 sufficient of the spermatic and plastic power to complete 

 even a larval form : some crude materials of the embryo 

 are the sole result : teeth, it may be, or hair, with irregular 

 amorphous ossifications, such as are met with occasionally 

 in ovarian cysts. 



The completion of an embryonic or larval form by the 

 development of an ovarian germ-cell, or germ- mass, as in 

 the Aphis, without the immediate reception of fresh sper- 

 matic force, has never been known to occur in any verte- 

 brate animal. 



The condition which renders this seemingly strange and 

 mysterious generation of an embryo without precedent 

 coitus possible, is the retention of a portion of the germ- 

 mass unchanged. One sees such portion of the germ-mass 

 taken into the semitransparent body of the embryo Aphis, 

 like the remnant of the yelk in the chick. I at first thought 

 that it was about to be inclosed within the alimentary canal, 

 but it is not so. As the embryo grows it assumes the 

 position of the ovarium, and becomes divided into oval 

 masses and inclosed by the filamentary extremities of the 



