DROSOPHILA AMPELOPHILA LOEW BRED IX THE 

 DARK FOR SIXTV-XIXE GEXERATIOXS. 1 



FERXAXDUS PAVXE. 



In a short note fBiuL. BULL., '10) I stated that I had been 

 breeding Drosophila in the dark for forty-mar .genera t ions or 

 nion- than two j that the darkne-s had produced no visible 



Ct either in the color of the body or in the structure of the 

 : but th.it thi-iv -eemed to be a difference in their reactions 

 to light, the Ones bred in the dark react in- more ^lowly than tl 

 bred ill the livjit. The e\ idence on which tin- la-t statement 

 was based \\a- \\ It \\.i-, obtained by placing a number of 



Ilie- in a clean \ ial and then iv\ol\ -\\\ \\ 50 as to brin^ lir-t one 

 end and then the other toward tin- li-ht. In tliis way it was 

 demonstrated thn the the- bred in the dark were noticeably 

 much -louer in theii ions than tho-,,- bred in the li^lit. 



These observations as far as they went \\ irrect, bul as we 



-hall 866 they uei'e not extensh ' an I hence led loan 



i i roneoua 'ttion. 



I ha\e iust linished :i -nt in which each lly was te 



indi\ idualK'. I'hi- inieiit ua- ba-ed upon four Aeries of 



llie-, I .000 in each ;i ,. I , dlOSC bred ill the 



dark for sixty-nine generations jeries no. 2), th 



bi'ed ill the dark lor -i\tv-loiir ^em-rat ion-, and then placed in 

 tin- liijit tor -i\ -t iieratioii-; third -erie- no. 3), tho-e bred otil\- 

 in the li:<ht: and fourth . new --train from series 



m>. .1 bred in the dark for live o-iieration^. 



The apparatus for testing each ll\- coiiMMed of a \\"eUba. h 

 lamp, .t h. reen three inche^ thick and a ^la<s tube one inch 



in-ide diameter and nine and three eighths inches luii;<. The 

 a|)paratn- \\a- arranged a-> -hown in the diagram l ; i-. l), the 

 end of the tube toward the lii;ht ln-in^ ten and three fourths 

 inches from it. Tin- Ua tube \\a- perfectl>" clean on the inside 

 and wrapped with black cloth on the out-ide. The llie^ \\ 



1 Cuntriluitimi limn th ical Lah- .tati-ry < >!" In liana triivrr-ity, No. 120. 



