THE URO-GENITAL SYSTEM 



405 



and into which the ductus deferentes empty. The lateral gen- 

 ital ridges unite to form the scrotal sac, and the point of union 

 between these is marked by a raphe. A median line of dark 

 pigment lies along the under side of the penis continuous with 

 the latter and marks the fusion of the lips of the genital 

 groove. Special muscles, also in part sexually homologous, 

 develop in connection with the external organs of both sexes. 

 These are composed of striated fibers and are more or less 

 under the control of the will. 



The elements of the indifferent stage and their differentia- 

 tions in the two sexes may be expressed in the following table, 

 which shows the sexual homologies. This table, taken in 

 connection with the one given above, for the internal parts, will 

 form a brief synopsis of the entire subject. 



