perpendicular to the surface, their outer ends being closed, and the medulla of 

 longitudinal tubes separated from one another by fibrous connective tissue. This 

 medullary portion is prolonged beyond the organ itself in the form of a band which 

 passes down the surface of the urinary bladder to the genital opening. Sections of 

 this band show that the longitudinal efferent tubes do not unite into a single duct or 

 vas deferens, but are only slightly reduced in number by coalescence, so that a large 

 number of tubes remain separate even to the external opening. Fig. 6 exhibits a 

 section of the cord or band connecting the testis with the exterior and containing the 

 separate efferent tubes. This section is more highly magnified than that shown in 

 Fig. 4, and is taken from the testis of a full-grown male preserved while in full genera- 

 tive activity, in March, 1889. The spermatozoa are seen within the efferent tubes, 

 completely filling the cavity of some of them, and appearing under a low magnifying 

 power as deeply stained granules : these granules are the heads of the spermatozoa, 

 the tails or vibratile appendages not being visible. 



If the cortical tubes in the section shown in Fig. 4 are examined under a more 

 powerful objective, each of them presents the structure shown in Fig. 5. At the closed 

 end of the tube are a number of large polygonal cells forming an epithelium. Each 

 of these cells has a large nucleus with many nucleoli ; lower down the tube is filled 

 with smaller and smaller cells produced by the division of the large cells. The large 

 cells are evidently constantly being multiplied by division, and after reaching a certain 

 size each is pushed down into the cavity of the tube where it divides and subdivides, 

 forming a cluster of smaller cells. In some parts of the tube such clusters of small cells 

 produced from a single original cell can be distinguished, but they easily break up and 

 the cells of various clusters are confused together. In some of the young clusters 

 near the closed end of the tube all the nuclei are seen in a state of di^dsiou showing 

 that each cell is dividing into two. 



The large cells at the closed end of the tube correspond to the germinal epithelium 

 of the ovary ; they do not extend down the sides of the tube, but are confined to its 

 end : they are the male germinal cells and from them all the spermatozoa are 

 produced. 



As the cells pass down the testicular tube they get smaller and smaller, and in the 

 lower ends and in sections of the deeper portions cut transversely they are seen to have 

 reached their limit of subdivision, for amongst them are seen deeply stained minute 

 spherical bodies which are the heads of spermatozoa. The minute cells produced 

 by continued subdivision are converted into spermatozoa and are called the 

 spermatoblasts. The details of the development of a spermatozoon from one of 

 these spermatoblasts can only be followed out by teasing up a portion of the testis on 

 a CTlass slide and examining it microscopically with the aid of reagents. The process 

 cannot be followed satisfactorily in sections because in these the elements are cut up 

 into pieces. I have not followed the process of development in the sole ; I will 

 therefore merely explain here that the protoplasm of the spermatoblast elongates 



