NON-DISJUNCTION OF SEX CHROMOSOMES 599 



I have been able to detect non-disjunction in certain other 

 stocks, notably eosin. Of the females tested, one gave the fol- 

 lowing offspring by a white miniature male. 



Fi eosin 9 white-eos. comp. 9 eosin c?' (long) white min.cf 



7 154 134 2 



These seven eosin females contained no trace of the paternal 

 white and miniature, for one mated to a wild male gave no 

 white or miniature sons, but only eosin not-miniature sons, and 

 further patroclinous sons, which were of course red. 



Pi eosin 9 (of the seven) wildc? 



Fi eosin 9 red 9 eosin cf redcf 



3 118 120 5 



The purity of the eosin daughters is shown even more clearly 

 by back-crossing three other females (of the seven) to white 

 miniature males. One would ordinarily expect half the males 

 and half the females to be miniature and white, with the pro- 

 portions showing the association of white and miniature. But 

 no such effect was produced, as one can see in the progeny: 



eosin 9 white-eos. comp. 9 eosincf white min.cf 

 15 133 135 9 



The white-eosin compound is a very efficient aid in studies 

 such as these, since it enables one to tell at a glance the com- 

 position of the female whether pure eosin, pure white, or white- 

 eosin; determining in this case that the thirteen daughters were 

 pure eosin and not-white, and that the 133 daughters were true 

 hybrids, i.e., white-eosin compounds. 



For the sake of maintaining stock, I have continued this line 

 a little further by breeding one of the three eosin females to one 

 of her red brothers. 



Pi eosin 9 redcf 



Fi eosin 9 red 9 eosin cf redcf 



5 81 76 6 



The next generation in the same manner was: 



eosin 9 red 9 eosin cf redcf 

 8 132 139 14 



