164 ELEMENTARY BIOLOGY. , [CHAP. 



a. Examine, with a low power. 



a. The organ is chiefly made up of tortuous 

 tubules, which are seen cut in various direc- 

 tions. 



b. Examine with a high power. 



a. Note the epithelium lining the tubules : it 

 varies with the season of the year (whether 

 before or after the breeding-time), and is usu- 

 ally extremely granular and ill-defined. The 

 cells are arranged in two or three rows, and 

 at the time of breeding the most superficial 

 layer of cells is transformed into spermatozoa, 

 each cell giving rise to several. These lie 

 side by side at right angles to the lumen of 

 the tubule, which accordingly appears to be 

 lined by them. 



c. The spermatozoa (B. 10. a. y). 



1. The ovary. 



1. The structure of this organ is easiest made out 

 shortly after the breeding-time. Remove one of the 

 ovaries, place it in water, and make an incision into 

 it : it will be seen to contain a cavity, and projecting 

 upon the walls of this cavity and also upon the outer 

 surface of the ovary are numerous round eminences 

 of various sizes : these are ova in different stages of 

 development, and the large ones will be seen to have 

 become more or less pigmented. 



2. Tease out a bit of ovary in normal saline solution : 

 '"over, and examine with a low power. 



a. Note the ova, many much smaller than those 

 which were seen (i) with the naked eye : they 



