REPRODUCTION IN DROSOPHILA. 



219 



process is repeated in the spermathecae. Here it is still easier to 

 follow their entrance, for the ducts of these receptacles are very 

 thin and transparent. In no case were spermatozoa observed 

 entering these receptacles before the ventral receptacle was filled 

 with spermatozoa. This might be explained by the position of 

 the orifice leading to the latter, which, as already stated, is placed 

 a little posterior to the openings of the spermathecse, and per- 

 haps also by the partial closure of the orifices leading to these 

 organs. 



The spermatozoa contained in the seminal receptacles form 

 bundles; in the ventral receptacle all the heads are directed 

 toward the tip or free end of the organ. In the spermathecse the 

 bundles are concentric. 



Once within the receptacles the spermatozoa cease to swim, 

 showing only undulatory movements; in this condition they can 

 live for many days, even weeks. 



5. THE EGG AND ITS ENTRANCE INTO THE UTERUS. 



The eggs of Drosophila melanogaster are very small, elliptical 

 in shape and bear at one end a pair of diverging appendages 



FIG. 7. Dorsal and lateral views of the egg of D. melanogaster. a, appen- 

 dages ; c, plate formed by the edge of o, transparent area resembling an oper- 

 culum ; m, micropyle cone. 



