Heart Drugs 



335 



The authors have also made a study of some galenical prepara- 

 tions and more particularly of tincture of digitalis in respect to 

 their toxicity for lupinus albus. It was found that various dilu- 

 tions of tincture of digitalis containing the same amount of alco- 

 hol were progressively less toxic for the lupinus so that a curve 

 could be plotted expressing the relationship between the toxicity 

 of the various concentrations and the growth of the plant, run- 

 ning more or less parallel to a similar curve obtained for the 

 toxicity of digitalis by the cat method. 



162 (2122) 



An effect of x-rays on crossingover in drosophila. 

 By JAMES W. MAVOR. 



[From the Department of Biology, Union College. Schenectady, 



New York.] 



In Drosophila melanogaster when a white-eyed, long-winged 

 female is crossed with an eosin-eyed, miniature-winged male, 

 the daughters are all heterozygous and may be represented by 

 w M 



the formula , indicating that one of the X chromosomes 



W e m 



carries the determiners for white eye-color (w) and long wings 

 (M) while the other carries the determiners for eosin eye-color 

 (W e ) and miniature wings (m). If such a heterozygous female 

 is bred she will have four kinds of regular sons irrespective of 

 the male with which she is crossed, since the regular sons obtain 

 their X chromosomes from their mother only. In two of the 

 kinds of sons the characters will appear as they entered in the 

 original cross, i. c, one kind will be white-eyed and long-winged 

 and the other eosin-eyed and miniature-winged; these make up 

 the noncrossover classes. In the other two kinds of sons the 

 characters will be interchanged, i. e., one kind will be white-eyed 

 and miniature-winged and the other eosin-eyed and long-winged; 

 these make up the crossover classes. It is usual in work on 



