156 J. T. CUNNINGHAM. 



the ovary, J. Brock lias described the fat-cells as empty follicles 

 of which the germ-cells have aborted. He states that in a 

 testis of Myrus he saw near the empty follicles altered germ- 

 cells which were opaque and had lost their nucleus^ and con- 

 siders that this leads to the conclusion that in the empty 

 follicles the germ-cells have disappeared altogether. He 

 proceeds to state that in osmic acid preparations the conclusion 

 becomes a certainty, for the follicles in these are usually not 

 empty, but contain shrunken cells which have reduced the 

 osmic acid very strongly as only fat and nerve-cells usually do. 

 He infers that the gerra-cells have undergone a fatty dege- 

 neration. It is clear enough that all this is better explained 

 by the simple fact that what Brock calls follicles are merely 

 true fat-cells, developed in the connective tissue, since evidence 

 that abortive germ-cells turn into fat is entirely wanting. 

 With the development of the adipose tissue, the testis, like the 

 ovary, becomes much larger in comparison with the younger 

 fatless stage, and therefore there is no reason to suppose that 

 the germ-cells, although they are scattered, have been reduced 

 in number. Fig. 35 shows the proximal portion of a section 

 of a testis of the conger in the adipose condition, as seen under 

 a low power. At the base of the section is seen the lumen of 

 the vas deferens. The total breadth of the testis, whose structure 

 is shown in this figure, from the attached base to the distal 

 edge, was about 5 mm. 



As the testis becomes more developed the narrow cords of 

 germ-cells or spermatogonia, seen in section in fig. 35, become 

 much enlarged, and form spermatic tubes filled with spermato- 

 cytes, of which those in the centre are smallest, and therefore 

 most advanced in development. The tubes are still separated 

 by a certain amount of adipose tissue, especially near the 

 distal edge of the organ, while near its attached base they are 

 more closely approximated. This is the condition observed in 

 sections of an organ about 7 mm. broad. In a much larger 

 organ, something over 1 cm. broad and 5 mm. thick from side 

 to side, there is still some adipose tissue between the large 

 tubes crowded with spermatocytes. But as I have shown in 



