214 T - H - MORGAN AND SABRA COLBY TICK. 



The FI generation of the reciprocal cross was published in 

 Science, 1912.' The rudimentary-winged female bred to a long- 

 winged male gave 381 long-winged daughters and only 3 rudi- 

 mentary-winged sons where equality was expected. Whether 

 the lack of sons here is due entirely to viability, or to other 

 conditions as well cannot be stated. 



In a very brief paper in 191 1 2 some other data were given that 

 showed the rudimentary classes running behind expectation. 

 These data were corrected and expanded in another paper, 3 

 to which reference may now be made. An F 2 count is given 

 there, that is an extension of the data published in the first paper 

 referred to above. There are 14,309 long-winged grandchildren 

 (cfcf and 99) and 115 males with rudimentary wings. The 

 expectation here is that one third of 14,309 or 4,769 flies should 

 have rudimentary wings. The entire number is 115, or only 1/41 

 of the expected number. 



There is an FI count of the reciprocal cross when 68 long-winged 

 daughters and 3 rudimentary -winged sons appear. This ratio 

 is not lower than that given above, and may safely be ascribed 

 to viability. In the F 2 count of the same combination the fol- 

 lowing classes and numbers were realized : 



Long 9 721 



Long d* 698 



Rud. ? . . . . . 163 



Rud. cf. . . ... 237 



The expectation is for equal numbers. The rudimentary 

 males, while far behind expectation, are not so far behind as in 

 other crosses cited, which is due to better treatment. This same 

 statement applies to the remaining data of the 1912 paper 

 for, at that time realizing more fully the influence of the environ- 

 ment on viability larger bottles with more food were used. Since 

 most of the data involves miniature wings it is not cited here. 



In the new experiments rudimentary-winged males were bred 

 to long-winged (wild) females; and long-winged daughters and 

 sons obtained. The daughters were then back-crossed to rudi- 

 mentary males either in pairs or en masse. When bred en masse 



1 Science, Vol. XXXIX'., March 22, 1912. 



2 Proc. Soc. Exp. Biol. and Medicine, VIII., February, IQII. 



* Zeit. f. induktive Abstammungs und Vererbunglehre, VII., 1912. 



