THE REPRODUCTIVE SYSTEM. 



653 



long pointed head, at the base of which is (b), an elliptical structure 

 joining the head to (c), a long filiform body; (d), a fine filament, much 

 longer than the body, is connected with this latter by (e), a homogene- 

 ous membrane. 



The head, as it appears in the fresh specimen, has a different refrac- 

 tive power from that of the rest of the organism, and with a high power 

 appears to be a light green color; there is also a central line running up 

 it, from which it appears to be hollow. 



FIG. 410. 



FIG. 441. 



FIG. 440. Spermatic filaments from the human vas deferens. 1, magnified 300 diameters; 2, 

 magnified 800 diameters; a, from the side; 6, from above. (From KOlliker.) 

 FIG. 441. Spermatozoa. 1, Of salamander; 2, human. (H. Gibbs.) 



The elliptical structure at the base of the head connects it with the 

 long thread-like body, and the filament springs from it. 



Whilst the spermatozoon is living, this filament is in constant mo- 

 tion; at first this is so quick that it is difficult to see it, but as its 



