08 THE EAETHWOEM 



situated in each median vesicula seminalis, the 

 open mouths being turned towards the testes, 

 and almost enclosing them. Their narrow ends 

 perforate the hinder septa of their respective 

 segments (x. and xi.), and are continuous with 

 the vasa efferentia. 

 d. The vasa deferentia. Prom the posterior end of 

 each seminal funnel a fine convoluted tube, the 

 vas efFerens, runs outwards and backwards on the 

 ventral body-wall. The two vasa efferentia of 

 each side unite in segment xii., and the duets so 

 formed run back to open to the exterior by the 

 apertures already seen on the ventral surface of 

 segment xv. The ducts are slightly imbedded in 

 the body-wall, and their exposure requires care. 



8. Microscopical examination of the reproductive organs, 

 and of their contents. 



a. The ovaries. Remove an ovary entire ; stain with 



carmine or magenta, and mount m glycerine ; or 

 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 iiuoleolus. The nucleolus is 

 stained by carmine more deeply than the rest of 

 the cell. 



b. The receptacula ovormn. Remove one and examine 



it as above. 



Ova may be seen in it at certain seasons. 

 . c. The contents of the spermathecse. Bemove a sperma- 

 theca and transfer to a slide. Tease in water 

 and examine. 



The seminal fluid in the spermathecsB con- 

 tains innumerable mature spermatozoa, each of 

 which is an exceedingly fine filament with a 

 slightly thickened head at one end. 



