REPRODUCTION IN DROSOPHILA. 217 



blooded), I per cent, solution of potassium citrate, 1 and I per 

 thousand solution of sodium hydroxide. All of these fluids in- 

 jure the spermatozoa more or less rapidly, and fail to keep them 

 alive beyond two or three minutes. On acount of the small size 

 of the flies it was not possible to obtain body plasma in sufficient 

 amount to tease the uterus in it and observe the behavior of the 

 spermatozoa. 



The spermatozoa do not enter the seminal receptacles imme- 

 diately after ejaculation has taken place. There is a pause which 

 usually lasts two or three minutes or even more, during which 

 the cavity of the uterus is packed with spermatozoa while the 

 seminal receptacles are entirely empty. This peculiarity was ob- 

 served once, and again in the uterus of flies killed after ten or 

 eleven minutes of copulation. These results are consistent with 

 those obtained by the study of sections of flies preserved at the 

 same stage, the spermatozoa being crowded in the uterine cavity, 

 while the receptacles and their ducts do not show any sperma- 

 tozoon whatsoever. 



The occurrence of this pause suggests that some change must 

 take place that causes the spermatozoa to swim actively, for the 

 swimming movements are very conspicuous when they enter the 

 receptacles in contrast to their almost passive condition while in 

 the uterus. This fact points to an influence on the part of the 

 parovaria which are the only accessory glands in the female geni- 

 talia whose function is obscure. Their bearing on the formation 

 of the shell of the egg is very doubtful, the latter being com- 

 pletely formed when entering the uterus. Lowne thought that the 

 parovaria in the blow-fly furnish the very young oocytes ; he 

 reached this striking conclusion on account of the presence of 

 certain structures in the cytoplasm of their cells which he com- 

 pared with the oocyte of mammals since they are surrounded with 

 a thin layer resembling the zona pellucida of the mammalian egg. 

 As already mentioned these curious structures are also present in 

 the parovaria of Drosophila. Lowne's interpretation is not war- 

 ranted by any fact, other than a superficial resemblance, the two 



i According to Koltzoff, 1908, the spermatozoa of the rhinoceros beetle, 

 Oryctes nasicornis. may be kept alive in a 2 per cent, aqueous solution of 

 potassium citrate for a week ; this observer thinks that their death is caused 

 by the growth of bacteria in the fluid rather than through exhaustion. 



