400 HARRY H. CHARLTON 



middle-piece or to see where the nucleus leaves off and the tail 

 filament begins, as the latter structure becomes finer and more 

 transparent until it is almost impossible to see where it ends. 



Text fig. A Mature spermatozoon of Lepisma domestica arranged from suc- 

 cessive camera-lucida drawings. X 2800. 



I have noted a tendency for the tails of the living spermatozoa 

 to stick together. The spermatozoa are very long, measuring 

 from 400 to 660/i. 



