Maech 17, 1922] 



SCIENCE 



295 



vin and the New England "lee Saints" (May 

 10) seems to be a similar fiction, according to 

 the late Waldo E. Forbes. Where such irregu- 

 larities appear in the mean of a number of 

 years, they appear to be the result of one or 

 more extreme occurrences. 



The well-merited praise that Professor Ward 

 bestows upon the new temperature charts of the 

 Atlas of American Agriculture could equally 

 well be turned by others upon his own splen- 

 did discussion of them. 



C. LeRoy Meisinger 

 "Washington, D. C. 



SPECIAL ARTICLES 



THE PRODUCTION OF NON-DISJUNCTION 

 BY X-RAYS 



In a previous issue of this journal^ the 

 writer described certain experiments which 

 showed that the X-ehromosome could be "elimi- 

 nated" from the egg of Drosophila by X-rays. 

 In these experiments red-eyed, homozygous, 

 virgin females were X-rayed and crossed with 

 white-eyed males. A total of twenty-four ex- 

 ceptional sons (white-eyed) were produced by 

 the X-rayed females; fourteen out of the nine- 

 teen fertile X-rayed females producing excep- 

 tions. All excepting one of the twenty-four 

 exceptional sons obtained from the X-rayed fe- 

 males were from eggs laid within six days of 

 the time of X-raying and they could be divided 

 into two groups con'esponding to eggs laid 

 during the earlier and later part of this period. 

 Plough- has shown that maturation of the eggs 

 in Drosophila melanogaster occupies approxi- 

 mately six days. It therefore seems probable 

 that the X-rays act on the eggs while in one of 

 the maturation divisions. 



In the experiments referred to above only 

 exceptional sons were recorded. In primary 

 non-disjunction as investigated by Bridges^ 

 both exceptional sons and exceptional daughters 

 occur. When, however, the female parent is 

 homozygous for the dominant allelomorph as 

 in the case of the X-ray experiments, the ex- 



1 Science, jST. S., Vol. LIV, September 2.3, 1921. 

 = Jour. Exp. Zool., Vol. 24, No. 2, 1917. 

 ?• Genetics, Vol. 1, p. 1-.52, 107-163, 1916. 



ceptional daughters are indistinguishable ex- 

 ternallj^ from their regular sisters. 



The experiments to be described were planned 

 to determine whether exceptional daughters 

 were produced as a result of X-rays. Accord- 

 ingly homozygous white-eyed i^emales were 

 crossed to eosin-ej^ed miniature-winged males. 

 The regular offspring of such a cross are eosin- 

 eyed, normal-winged daughters and white-eyed 

 normal-winged sons. The exceptions are white- 

 eyed, normal-winged daughters and eosin-eyed, 

 miniature-winged sons. In the experiments, 

 white-eyed, virgin females from stock obtained 

 from Dr. T. H. Morgan and used in the pre- 

 vious X-ray experiments, were mated to eosin- 

 eyed, miniature-winged males from stock ob- 

 tained from H. H. Plough. The females used 

 both for the controls and for X-raying, were 

 all sisters, being from the first generation of a 

 single pair of white-eyed flies. The virginity 

 of these was secured by isolating pupse in test 

 tubes. The X-raying* was done soon after the 

 flies emerged from the pupa cases and they 

 were immediately mated. The males used in 

 the matings were, in the greater number of the 

 experiments, the offspring of a single pair of 

 eosin-eyed, miniature-winged flies. (This was 

 probably an unnecessary precaution). Seven- 

 teen of the control jjairs were fertile and one 

 pair or 6 per cent, produced one exceptional 

 son (eosin-eyed and miniature-winged). The 

 total number of offspring produced by the con- 

 trol pair's in the first generation was 1,743 fe- 

 males and 1,726 males and the exceptional fly 

 formed .06 per cent, of the males. Thirteen of 

 the X-rayed females were fertile. Nine of them 

 or 69 per cent, produced exceptions, two 

 daughters (white-eyed and normal-winged like 

 Iheir mothers) and twelve sons (eosin-eyed 

 and miniature-winged" like their fathers). The 



* The X-ray dosage and the technique of these 

 experiments cannot be adequately described in a 

 short note such as the present. They will be 

 described in detail in a more extended paper to 

 appear shortly. 



t> In the case of three of the exceptional sons 

 tlie wing character was not determined. Two of 

 them were obtained by dissecting late pupal stages 

 and one died before its wings had expanded. . 



