21 6 JOSE F. NONIDEZ. 



little nearer the vagina than the openings of the spermathecae 

 (/), and this position seems to have some relation to the entrance 

 of the spermatozoa into the receptacles and their discharge at the 

 time of fertilization. 



Besides the organs described there are two other organs (Figs. 

 3 and 9, />) which correspond in structure with the so-called 

 parovaria in other forms (Lowne, 1893). These organs are ob- 

 viously glands; they possess a cavity filled with a colloidal fluid 

 containing minute refractive granules. They are connected with 

 the anterior portion of the uterus by means of ducts, which open 

 near the orifices of the spermathecae (Fig. 5, />'). The walls of 

 the parovaria are made up of large cells which contain round 

 nuclei and a peculiar structure, described in Calliphora by Lowne 

 and erroneously interpreted by this observer as a future egg. 



In virgin females the wall of the uterus collapses, the lumen 

 being quite narrow and irregular. 



3. THE EJACULATION OF THE SPERM AND ITS ENTRANCE INTO 



THE SEMINAL RECEPTACLES. 



The observation of the living uterus and the study of sections 

 of flies killed at different periods during mating showed that the 

 ejaculation of the sperm usually takes place about nine or ten 

 minutes after the beginning of copulation. 



Female flies killed immediately after the ejaculation of the 

 sperm showed that, although most of the spermatozoa seemed to 

 be motionless at this time, they occasionally exhibit faint un- 

 dulatory movements. If they do not move freely it may be be- 

 cause the mass of spermatozoa is subjected to the pressure exerted 

 by the walls of the uterus or possibly to a considerable extent 

 because of the viscid condition of the fluid portion of the ejacu- 

 late. But it is evident that they are at least potentially active, as 

 shown by their behavior in later stages. 



It was not possible to study the movements of the spermatozoa 

 when outside of the uterus, the fluids foreign to the body causing 

 at first a decrease in their activity, followed by their death. I 

 have dissected flies in several fluids such as tap and distilled 

 water, normal saline solution (0.5 per cent.), Ringer's fluid (cold- 



