M. C. Kobin on the Sexual Deferences of Eels. 389 



make it pass into the state of milt at the time of the produc- 

 tion of spermatozoids. 



Out of the period of reproduction the seminiferous tubes are 

 0-08-0-09 millim. in thickness, cylindrical, twisted in various 

 directions, and ramified once or twice. Some of them 

 anastomose with their nearest neighbours. Their extre- 

 mities are closed, rounded, with or without a slight inflation. 

 For the most part one of the extremities is situated close to 

 the surface of the organ, which is covered with a delicate 

 peritoneal tunic. None of them is particularly directed towards 

 the deferent canal, and none opens into the latter. 



The flexuosities of the tubes, their volume, and their struc- 

 ture give to the tissue of the organ the characteristic arrange- 

 ment and the aspect usually observed in the testicular tissue of 

 the higher Yertebrata. It is only by an enormous dilatation 

 at the breeding-season that we can imagine that these canali- 

 culi arrive at the state of seminal cajjsules. 



These tubes are immersed in a dense web of cellular tissue, 

 without adipose vesicles, and of a thickness between the tubes 

 about half that of the latter. The ramifications of the 

 vessels coming from the base of the lobes run along by the 

 tubes and form around each of their extremities, rounded at 

 the surface of the organ, a circular mesh 0*08 millim. in 

 breadth ; these altogether constitute an abundant network. 

 The examination of the entire lobe, before making thin sec- 

 tions, might lead one to suppose that these meshes circum- 

 scribe so many closed vesicles or seminal capsules, whilst we 

 have to do only with the extremities of the seminiparous 

 canalieuli. 



By the assistance of Dr. Hermann, preparator of the course 

 of histology of the Faculty of Medicine, I have been able to 

 ascertain that these tubes are composed of a delicate proper 

 wall (0*001 millim.), which is transparent and homogeneous, 

 folds readily, and is strongly adherent to the exterior tissue. 

 Their inner surface is uniformly lined with a single series of 

 regularly prismatic epithelial cells, with their outer surface or 

 base polygonal, which separate easily from the wall and are 

 attenuated at their inner extremity. They bound, in the direc- 

 tion of the axis of the tube, a narrow canal, which is often 

 apparently closed, in consequence of the contiguity of these ex- 

 tremities of the bounding-cells. The latter, which are finely 

 granular, contain a comparatively large hyaline nucleus with- 

 out granules, with a brilliant yellow nucleolus. The cells 

 which are immediately contiguous are broken by separation, 

 giving to the preparing fluid an opaline or lactescent appear- 

 ance ; floating in it are their shining yellowish granules and 



Ann. & Mag. N. Hist. Ser. 5. Vol. vii. 29 



