Linkage Data. 



25 



By adding the successive values from forked (i. e., f-T+T-s), triangle comes at 

 81.8 and short at 86.9. Neither of these is based on large numbers, however, and 

 consequently they are open to question. The second method involves the use of 

 the singed-short value, which is based on 1,442 flies. This would place short at 85.3, 

 which differs by less than 2 units from the other value. By working back from this, 

 triangle would be placed at 80.2. In contrast to these two lines of evidence, which 

 give essentially the same results, the other two deviate considerably, and in opposite 

 directions. The first is based on the forked-short value as given by experiments 45 

 and 48 (577 flies). These experiments are particularly significant, because both 

 involve singed, magenta, forked, and short simultaneously. According to these, the 

 forked-short distance is 18.5, placing short at 89.6, or 3 units beyond the more extreme 

 of the two values given above. 



The fourth method considered is that of using the forked-rugose value to locate 

 rugose (at 97.4) and then working backward to locate short and triangle. This 

 places short at 81.5 and triangle at 76.4, about 4 units less than the least extreme 

 value given above. Since the forked-rugose value, upon which these depend, is prob- 

 ably too short by about this amount, due to undetected double crossing-over, it seems 

 probable that the first two methods give approximately correct results. They also 

 represent roughly the average of the other values, and hence they are used in con- 

 structing the map. Triangle is thus placed at 81 (intermediate between 80.2 and 81.8) 

 and short at 86 (intermediate between 85.3 and 86.9). 



Cut. 



As noted above, cut appeared in a culture carrying short, and has behaved like an 

 allelomorph of short. The original female, heterozygous for cut, and either hete- 

 rozygous or homozygous for short, gave 23 cut and 26 short sons, wth no wild-type 

 or cut short sons. The daughters were all wild-type. Nine of these were tested 

 individually and proved to be of two types; 4 of them gave short sons and sons with 

 normal wings, but no cut, and 5 of them gave cut sons and sons with normal wings, 

 but no short (M 182, 197, 204, 206-209, 232, 234). Females heterozygous for cut 

 and carrying short in the opposite X-chromosome have been used in keeping the 

 stock of cut, and their sons have thus far been of the two types short and cut. 



D. H. HILL LIBRARY 



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