Vol. XXXIX. October, 1920. No. 4. 



BIOLOGICAL BULLETIN 



THE INTERNAL PHENOMENA OF REPRODUCTION 



IN DROSOPHILA. 



JOSE F. NONIDEZ, 



CARNEGIE INSTITUTION OF WASHINGTON, STATION FOR EXPERIMENTAL 



EVOLUTION. 



The present paper is limited to a description of the internal 

 phenomena of reproduction in the vinegar fly Drosopliila melano- 

 gaster, comprising under this title the ejaculation of the sperm 

 by the male, its storage in the seminal receptacles of the female, 

 and the discharge of the spermatozoa from the latter, at the time 

 of the fertilization of the eggs. 



The work was carried out in the Marine Biological Laboratory 

 at Woods Hole during the summer of 1919 at the suggestion of 

 Professor T. H. Morgan, to whom I am indebted for advice and 

 helpful criticism, also for valuable information gathered by him 

 in his attempts to bring out artificial fertilization in this fiy. An 

 obstacle in the study of the experimental fertilization in Droso- 

 phila is the high sensitiveness of the spermatozoa to the action of 

 fluids foreign to the body; they are easily injured and killed 

 when placed in mixtures which do not exert noxious effects on 

 the sperm of other animals, unless the spermatozoa are kept in 

 such fluids for a long time. Although I tried repeatedly to elim- 

 inate this obstacle by the use of several called " indifferent " 

 fluids, it was impossible to keep the spermatozoa active beyond a 

 few minutes. 



During these experiments I gathered interesting data on the 

 normal reproduction of Drosophila, in which, owing to the small 

 size and transparent condition of the internal generative organs, 



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