GENES MODIFYING NOTCH. 



379 



stock, so that only yellow prune flies could be utilized to again test this 

 cross. The results confirmed the earlier ones, as seen in table 16. 



The flies in all but one culture (No. 4) give nearly the same results 

 as do the short Notch short females bred to then* own stock males. 

 Either the same factor for short Notch is carried by yellow prune that 

 is present in the short Notch stock, or else some other factor that has 

 a closely similar effect. As yet I have not put this question to a test. 

 Culture No. 4 gave such a different result from the other five that it 

 is almost certain that the "short" modifier was absent in this case. 



TABLE 16. Short Notch 9 by yellow prune cf . 



ABERRANT NOTCH WINGS. 



In the course of the selection experiment a few individuals appeared 

 in which the wings showed an extreme condition of Notch. That 

 these rare cases were due to some abnormal condition that influenced 

 the development of the wing is shown by the fact that in most cases 

 only one wing was affected, as shown in the three cases drawn in figure 

 99, a, 6, c, and by the fact that when these were bred the offspring were 

 of the usual Notch type. When both wings were affected (fig. 90, a) 

 the flies were usually sterile. Possibly the results were due to somatic 

 mutation, but this is not very probable. Two of the three flies had 

 one normal wing, but the eye-color showed that the flies were gene- 

 tically Notch. Similar modifications were seen in the eosin ruby 

 sisters of these flies that did not contain the Notch-bearing gene. 



DEFORMED EYES. 



From time to time flies appear in the Notch stock in which one or 

 both eyes are reduced (fig. 100), sometimes to mere specks. All 

 attempts to breed such a type have been futile (although the males 

 at least are fertile) and all attempts to cause them to appear in larger 

 numbers by alterations in the environment (heat, cold, acidity, mois- 

 ture) have failed. The remnant of the eye arouses a suspicion that the 

 eye has been injured either by the larvae in feeding or else by shaking 

 the bottle containing the pupae. We meet, not rarely in other stocks, 



