2O8 JOSE F. NONIDEZ. 



it was possible to observe the contents of the extirpated uterus 

 and seminal receptacles of the fertilized fly in the living condi- 

 tion. These organs were kept under direct observation for some 

 time, and the entrance of the spermatozoa into the receptacles 

 and the position of the egg within the uterus were seen directly 

 instead of having to be inferred from series of sections taken at 

 different stages in these processes. Sections have been used as a 

 means of checking up the results obtained by direct observation. 

 Drosophila has thus provided almost unique material for the 

 study of the internal phenomena preceding normal fertilization 

 in insects, for besides the facts just mentioned, the mating of a 

 considerable number of flies can be easily brought about at any 

 desired time. 



i. TECHNIQUE. 



The wild stock of Drosophila inelanog aster was used through- 

 out the work. Virgin females isolated shortly after hatching 

 were mated to males of the same generation three or four days 

 after isolation. The matings were accurately timed in every case. 



The flies were either etherized or killed by a preserving fluid 

 while in copulation or as soon as this was finished. In the first 

 case the observations were made on the living genitalia, these 

 organs being dissected out under a binocular microscope in a drop 

 of Ringer's fluid or normal salt solution, after which they could 

 be observed with a high power microscope. In order to follow 

 the path of the spermatozoa into the receptacles and observe the 

 position of the egg within the uterus, no cover glass was added, 

 and in this way any pressure which might interfere with the first 

 process or crush the egg was avoided. If a cover glass is used 

 and gently pressed down with a needle, the ventral receptacle, 

 normally coiled, will straighten and its contents may be easily 

 observed under high power, the spermatozoa being readily de- 

 tected when present. 



The flies which were preserved were embedded in paraffin and 

 cut into sections. The specimens were always dropped alive in 

 the following fluid, after the formula of W. Docters van 

 Leeuwen : x 



i Zoo/. Am., Bd. 32, 1908. 



