74 THE EARTHWOEM. 



exterior by the apertures already seen on the 

 ventral surface of segment xv. The vasa de- 

 ferentia are slightly imbedded in the body-wall, 

 and their exposure requires care. 



3. Microscopical examination of the reproductive organs, 

 and of their contents. 



a. The ovaries. Bemove an ovary entire ; examine in 



salt-solution; then stain with carmine or 

 hcematoxylin, dehydrate, clear, and mount in 

 balsam. 



The proximal and thicker end of the ovary 

 is a solid mass of cells from which the ova 

 are formed : the distal portion contains ripe 

 ova. Each ovum is a large cell with very dis- 

 tinct nucleus and nucleolus. The nucleolus is 

 stained by carmine more deeply than the rest of 

 the cell. 



b. The receptacula ovorum. Bemove one and examine 



it as above. 



Ova may be seen in it at certain seasons. 



c. The contents of the spermothecse. Bemove a spermo- 



theca and transfer it to a slide. Tease it in salt- 

 solution and examine with low and high powers. 

 The seminal fluid in the spermothecse con- 

 tains innumerable mature spermatozoa, each of 

 which is an exceedingly fine filament with a 

 slightly thickened rod-like head at one end. 



d. The testes. Bemove a testis ; stain, dehydrate and 



clear it, and tease it in balsam : mount another 

 in salt-solution. Examine with a high power. 



The spermogonia are cells, each of which 

 by division gives rise to spermocytes. Only the 

 earliest stages of the division occur in the testes, 

 masses of spermocytes leaving them with numerous 

 nuclei and tuberculated surfaces. 



