406 



BOWEN. 



A 



C 



equal total length, but the large sperm have a 

 much hea\aer tail, near the tip of which is a 

 characteristic swelling. The head, on the other 

 hand, is exceedingly long but correspondingly 

 decreased in diameter, so that it is scarcely 

 more than a tliread. Smears of Evschistus 

 were also made, in which the three expected 

 kinds of sperm were very easy to distinguish, 

 the large ones pro\dng of extraordinary size. 

 Text-figure 5 gives an idea of the comparative 

 sizes of the three sperm classes. In these 

 figures the diameter of the sperm head has 

 been much enlarged in each case in order to 

 make the heads clearly e\'ident at such low 

 magnification. Actually, the large sperm head 

 is exceedingly delicate and thread-like, and not 

 at all like the figures given by Montgomery 

 ('10; figs. 24-26). According to Montgomery 

 the volume of the large and small sperm heads 

 differs markedly, and this difference was sup- 

 posed to depend on the fact that the chro- 

 matin exists in the sperm head as a peripheral 

 layer enclosing a quantity of karyolymph, the 

 latter determining the size of the head. My 

 observations do not corroborate these state- 

 ments in any particular. As will be pointed 

 out in a later section, and as I have showTi 

 previously (Bowen '22a) for the small sperm 

 of Mvrgantia, the head is probably a solid rod 

 of chromatin, and the appearance described by 

 Montgomery (if in mature sperms) is due to 

 faulty technique. As a matter of fact, in sec- 

 tions such as he used the heads are often made 

 to appear thicker than they actually are. As 

 indicated by smears, the volumes of the mature 

 sperm heads are probably very similar, allow- 



FiGURE 5. Mature sperms from the vas deferens 

 of Evschistus eiLSchistoides (x255). (Smear prepara- 

 tion; osmic fumes-hematoxylin.) A, from the small- 

 est generation; B, from the small or normal genera- 

 tions; C, from the large generations (the tail has 

 been bent in the drawing in order to save space.) 



