866 PROF. G. C. BOURNE ON THE ['NoV. 17, 



the left side of the body. Its relations are clearly seen in fig. 44. 

 It can be seen that the sperm-duct narrows somewhat on entering 

 the epididymis, forms a great number of very fine convolutions 

 on its left side, and passing to its hinder end increases appreciably 

 in diameter. The ultimate coils lie on the right side, are greatly 

 swollen and filled with spermatozoa. The last coil finally emerges 

 from the epididymis-sac close to where the sperm-duct entered it, 

 and immediately contracts to form a rather thick-walled tube, 

 which I shall call the middle tube. The sperm-duct before it 

 ■enters the epididymis is lined by small cubical ciliated cells. On 

 entering the epididymis the epithelium changes its character. 

 The cilia ai'e lost ; the cells become relatively large — in the 

 nari'ower coils three or four sufiice to surround the lumen of the 

 duct, — their cytoplasm becomes dark and granular and their 

 nuclei clear with a sparse chromatic reticulum. In the thick 

 terminal convokitions (fig. 55) the epithelial cells are very laige 

 and their cytoplasm is full of deeply-staining granules. So far 

 as I am able to judge, the spermatozoa mature during their 

 passage through the coils of the epididymis. In the follicles of 

 the testis and in the initial part of the sperm- duct they have 

 globular or ovoid heads, which do not stain deeply, and short 

 filiform tails. In the large terminal coils of the epididymis the 

 heads are elongate, stain intensely with hfematoxylin, and the 

 tails are longer and apparently thicker. They are, however, so 

 matted together that it is impossible to make out details. But it 

 is clear that the chromatin has increased in quantity and that the 

 spermatozoon, as a whole, has increased in bulk. The characters 

 of the epithelial cells are suggestive of the function of elaborating 

 material for the nutrition of the spermatozoa. In the middle 

 .tube the epithelium again becomes cubical and richly ciliated. The 

 middle tube passes into the genital complex, runs some way 

 forward in its wall, makes an abrupt turn backwards, and at once 

 enters a small thick-walled chamber which I shall call the 

 thalamus, as it evidently corresponds to the chamber into which 

 the oviduct opens in the female. 



There is very little pigment on the course of the sperm-duct in 

 the species of Paranerita that I have studied : if any is present 

 it is on the walls of the middle duct, but I have only observed 

 this in P. gagates. 



The thalamvis is a narrow and elongated chamber situated in 

 front of the posterior third and near the inner or left side of the 

 g-enital complex (figs. 44 &, 48, th.). It is lined by a very long 

 ciliated columnar epithelium sharply marked off" from the ciliated 

 lining of the middle tube of the sperm-duct. This abrupt passage 

 from one kind of epitlielium to the other indicates, I believe, the 

 boundary between the mesodermic and ectodermic structures. 

 Anterioi'ly and posterioily the thalamus receives the ducts of a 

 compact acinous gland which I shall call the prostate (figs. 48 ct 

 49, _p?'s.). It is clearly formed by evaginations from the wall of 

 the thalamus and has a distinct lumen. Its epithelial lining is 



