VII.] THE TESTIS. 223 



somewhat close connection with the Wolffian bodies; 

 but occupy about the same limits from before back- 

 wards. The mesoblast in the position we have men- 

 tioned begins to become somewhat modified, and by 

 the eighth day the testis is divided by septa of connec- 

 tive tissue into a number of groups of cells; which are 

 the commencing tubuli seminiferi. By the sixteenth 

 day the cells of the tubuli have become larger and 

 acquired a distinctly epithelial character. 



The history of the primordial cells in the male has 

 not been so thoroughly worked out as in the female. 

 The spermatozoa appear to arise by the division of 

 the primitive ova (present, as we have stated, in the 

 early stages of both sexes), which probably migrate 

 into the adjacent stroma, accompanied by some of the 

 indifferent epithelial cells. Here the primitive germi- 

 nal cells increase in number and give rise to the cells 

 lining the secretory tubules of the testes. 



Outgrowths from the Malpighian bodies of the 

 Wolffian body appear to be developed, which extend 

 into the testis and come into connection with the true 

 seminiferous stroma. 



It is evident from the above account that the male 

 and female generative products are homodynamous, 

 but the consideration of the development of the pro- 

 ducts in the two sexes shows that a single spermatozoon 

 is not equivalent to an ovum, but rather that the whole 

 of the spermatozoa derived from a primordial ovum are 

 together equivalent to one ovum. 



We have now described the origin of all the parts 

 which form the urinary and sexual systems, both of the 

 embryo and adult. It merely remains to speak briefly 



