en. iv THE GENEEATIVE SYSTEM OF THE MALE 121 



joining, form the germ (the fertilised ovum) in which are contained 

 the potentialities of the entire organism to be born, the deter- 

 minants of the entire ulterior development, and all the rudiments 

 of the hereditary characters of the two generations. 



Towards the constitution of the germ, the whole organisms of 

 the parents co-operate in a process ever mysterious, and it is on 

 this account that generation or reproduction, although it is carried 

 out by means of special sexual apparatus, can and logically must 

 be considered as a most important integral part in the 

 physiology of the organism as a whole. 



Faithful to our programme of keeping within the limits of the 

 physiology of man, we must refer the reader to treatises on botany 

 and zoology for the study of the various forms and modes of 

 agamic and monosexual generation (division, gemmation, un- 

 fertilised ova or parthenogenesis} and confine ourselves exclusively to 

 the study of bisexual generation (fertilisation of the ovum of the 

 female by means of the spermatozoon of the male) which is 

 observed exclusively in the higher animals and man. 



I. During embryonic development both the male and the 

 female sexual apparatus appear as generative layers in which no 

 sexual difference can be recognised. Only at a given period of 

 development are differences evolved which indicate masculine or 

 feminine characters. The different parts of the embryonic genital 

 apparatus then acquire a special form, structure, and relations in 

 the two sexes: some develop and become of great importance, 

 others atrophy or remain rudimentary. It is, however, always 

 possible with the data furnished by embryology to reduce to a 

 common fundamental type the sexual apparatus of the two sexes, 

 and to discover the homologies between male and female parts. 



The testicle is the homologue of the ovary, the vus deferens of 

 the oviduct ; the vagina and uterus of the female are homologous 

 to the utriculus prostaticus, a quite rudimentary organ called by 

 Weber the male uterus ; the clitoris corresponds to the penis ; the 

 labia majora to the scrotum. These homologies explain the 

 so-called cases of hermapkroditism in mammals and man described 

 by the ancients. It is not a question of true but only of apparent 

 hermaphroditism, due to some parts reaching an exaggerated 

 development, while others are incomplete, and thus resemble the 

 parts of the opposite sex. 



The essential organs of the male genital apparatus are the 

 testicles, because in them are formed the sexual cells of the male 

 which are named spermatozoa (zoosperms, spermides, or spermatic 

 filaments). 



In section (Figs. 17, 18) the testis is seen to be formed of a 

 parenchyma surrounded by a fibrous capsule, the tunica albuginea, 

 which at the posterior border of the organ becomes thickened 

 to form the mediastinum testis, or corpus Highmori. From this 



