706 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The prostate glands are stated by KoUiker to make their appear- 

 ance at about the third month in the human embryo; in reality, 

 they appear somewhat earlier, about the second month ; in a 

 previous investigation carried out in conjunction with M. Eobin, it 

 was found that the prostate glands form a system entirely inde- 

 pendent of their ducts and of the ejaculatory canals ; and the present 

 research confirms this idea; the prostate also is not connected 

 with the urinary apparatus, as it was said to be by Virchow, but 

 with the genital system; it is comparable to the glands of the 

 urethra in the female ; the entire urethra in the female is conse- 

 quently homologous with the prostatic portion only of the male 

 urethra, while the penial portion, including Cowper's glands, cor- 

 responds to the vulva in the female. 



The external genital organs are fully formed at a somewhat 

 earlier date in the male than in the female ; at three and a half 

 months they are very nearly complete in the male, while in the female 

 at this period there is still a slit uniting the urethra with the vagina ; 

 a complete separation is accomplished after four months. 



Spermatogenesis.* — MM. Swaen and Masquelin have published 

 their very interesting observations on the developmental history of 

 spermatozoa, in continuation of the work of Lavalette St. George. 

 To understand the work of the later observers, it is necessary to 

 recapitulate St. George's conclusions. They are as follows : — Sper- 

 matozoa originate in special cells, very similar to young ovules, 

 which may be called spermatogonia. These elements multiply and 

 form groups of small cells, spermatocytes, which remain grouped 

 together so as to constitute f-permatogems. At the periphery of the 

 spermatogems a certain number of spermatocytes are modified so as 

 to form a membranous envelope, a cyst (amphibians and insects). 

 In other cases (Selachians), a single spermatocyte is modified at the 

 base of the spermatogem and forms the basilar cell. In mammals, 

 on the other hand, the spermatogem developes neither a cystic 

 membrane nor a cystic basilar cell. It is the spermatocytes which 

 are transformed into spermatozoids. 



In addition to these elements there occurs a second kind of cell, 

 forming a more or less complete envelope for the spermatogonia. 

 These follicular cells play only a very secondary part in sperma- 

 togenesis, eventually disappearing. 



MM. Swaen and Masquelin conducted their researches on the 

 testicles of ScylUum catulus, the salamander, and the bull. 



In ScylUum, the seminiferous ampullae of the testicle (cf. Graafian 

 follicles) contain groups of two kinds of cells, (1) the central sper- 

 matogonium or male ovum, a large nucleolo-nucleate cell partly in 

 contact with the adjacent connective tissue, partly bounded by (2) the 

 smaller, oval or irregularly shaped, follicular cells. As the " male 

 ovule " multiplies (by indirect cell-division), the follicular cells also 

 multiply and force their way inwards between the resulting daughter- 

 cells of the spermatogonium to finally form a bilamellar body 



* Arch, de Biol, iv. (1883) pp. 749-802 (5 pis.). 



