THE NERVOUS SYSTEM. 75 



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

 method. 



1. Remove a portion of one of thevesiculffi 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 

 cells {i.e. to coagulate the protoplasm of the 

 cells). 



8. Warm very gently over a flame until the prepara- 

 tion begins to dry. Then cover with a drop of 

 dahlia solution ('25 per cent.) and allow to stain 

 for three minutes. 



4. By means of a pipette wash with water and mount 



in a drop of glycerine on a slide. 



5. Examine under the microscope and draw the 



several stages shown. 



The vesiculfe contain spermatozoa in all stages 

 of development : — (1) the massed spermocytes 

 as they leave the testis ; (2) a stage in which the 

 tubercles, or spermatids, are more distinct and 

 are produced outwards into filaments ; (3) later 

 stages in which the filaments are elongated to 

 form the tails of the spermatozoa, while the bodies 

 of the spermatids form their rod-like heads. 



A part of the spermocyte-mass remains un- 

 changed in the centre of the mass and is called 

 the blastophore. 



F. The Nervous System. 



This consists of a ventral cord, swollen slightly in each 

 segment ; and a pair of dorsal ganglia in front, connected with 



