486 



THE AMERICAN NATURALIST [Vol. LV 



Mateeial and Methods 



The flies furnishing the data set forth in this paper be- 

 longed to five different basic laboratory stocks or strains 

 of Drosophila melanog aster. Four of these stocks were 

 obtained from Professor T. H. Morgan in December, 

 1919, and have been bred continuously in this laboratory 

 since that time. The original individuals of the fifth 

 stock were collected by one of us (R. P.) as wild flies at 

 Eagle Point, Lake Memphremagog, Vermont, in the sum- 

 mer of 1920. 



The stocks may be listed as follows : 



1. Old Falmouth. Wild t.yi)e fly, lonj? bred in Morgan's laboratory. 



More inbred than 2. 



2. New Fdlmou-lh. Wild type fly bred for about 6 months in Mor- 



gan's laboratory before we got our sample of it. 



sepia eyes, in homozygous form. Other characters wild types. 

 (Morgan.) 



4. QuiniupU. A synthetic =;tock, carrying five s.^cond chromosome 



mutations, each in homozygous fonn, as follows: Purple, 

 arc, speck, vestigial, and black. Other characters wild tyi>fc^ 

 (Morgan.) 



5. Eagle Point. Wild type collected in summer of 1920, and since 



bred in this laboratory. 



An account of the second chroniosonie mutations unm- 

 tioned will be found in Hri.luvs luul Mor.unii (19) nud 

 Sturtevant (20). The (li>.-nv.'r\ of the iimt;ill.>ii -.'Ih.-i 

 noted by Muller (21). 



The stocks are carried along in the laboratory in pure 

 mass cultures in half-pint milk bottles. Those in an ex- 

 periment on duration of life are tested relative to this 

 character in one ounce shell vials. 



The flies are all kept on a standard food mixture made 

 up fresh each day, according to the following method: 



For each 100 c.c. of water ndd 2 grjun^ of agar-agar. Boil the 

 agar and water until the :igMr tl.umu-lily (]i..,,lvr.l. For each 

 100 c.c. of solution add KtO j^t mu^ l ij,.. pr. !,.! .n;i<lir,l bananas. 

 Boil five minutes. Pour inn- l..ti|,. uhirh l,;n,- U,n u. ll heated in 



3/4 inch deep; in duration of life b(>ttle> a layer 1 2 Inch d<vp. AVhen 



