26 



Tanaka. 



The facts aliove stated are sufficieut, as I believe, as the proof 

 for occurreiice of 3 : 1 : 1 : ."5 (in a single ease, however, 2:1:1:2) 

 coupling in the male MYmij animals. 



No families from the reciprocal cross MYmy 9 X mymy c? are 

 reared as yet in my expei'iments, and therefore we cannot tell till the 

 next season what actually occurs in the ovogenesis of iliF»«?/ individuals. 

 There is, however, liigh prol »ability for existence of a complete coupling 

 between M and Y in the female hybrid. The supposition stands upon 

 two facts. Firstly, a complete reduplication occurs in NynY female, 

 while a low i)artial takes place in NynY male, and analogy may per- 

 haps be ai)i)licable to M-Y coupling. Secondly, the zjgotic ratio as 

 mentioned already, where the male gametic distribution is 3:1:1:3, 

 will be quite incomprehensible, if a complete or very high coupling was 

 not assumed to occur in the op])osite sex. Thus it is evident that 

 MYmy animals produce the following gametic series 



give rise to the 



1 1 MY : 1 My : 1 mY : 3 my. 

 Multijjly each term of the series by 15, then we will obtain 

 16.5 MY : 15 My : 15 mY : 45 my, 

 a system considerably close to the ratio 



177 : 15 : 15 : 49, 

 which is the outcome of the gametic series (7:1:1: 7). 



The actual results are comjjared with the theoretical numbers 

 calculated on the 11 : 1 : 1 : 3 liasis below. 



