82 THE EARTHWORM 



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. Remove one and examine 



it as above. 



Ova may be seen in it at certain seasons. 



c. The contents of the spermothecse. Remove 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. Remove 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 tuber culated surfaces. 



e. The contents of the vesiculae seminales. Cover-glass 



method. 



1. Remove a portion of one of the vesiculae seminales 



to a slide, tease with needles and dilute to 

 three or four times its bulk with normal salt- 

 solution. 



2. By means of a pipette spread a small drop of this 



liquid evenly over the surface of a clean cover- 

 glass. Invert this and hold it over the mouth 

 of a bottle containing glacial acetic acid for 

 several seconds in order to kill and ' fix ' the 



