GENETICS PURPLE EYE COLOR DROSOPHILA 277 



case of vestigial the effects of preriiaturation and repugnance 

 were not as great in degree. On the basis of these results, an 

 analysis of the extent to which each of these principles con- 

 tribute to the 'inviabiUty' of vestigial was undertaken by G. L. 

 Carver (results not yet published). In Carver's investigation it 

 was assumed that the shortage in these experiments had been 

 largely due to a cause intrinsic to the vestigial itself, for which 

 reason any stock of vestigial should be equally valid for the test. 

 The stocks used in the above experiments were not used because 

 they were full of odds and ends of mutations which might lead 

 to confusion. The tests of Carver showed that very little pre- 

 maturation or repugnance is inherent in vestigial, the ratios 

 being exceptionally close to Mendelian expectation. Wherefore 

 it seems probable that the shortage met with in the purple 

 vestigial experiments was due to some cause peculiar to the 

 stocks used or to the culture methods used in the experiment. 

 Later tests with stocks descended from these original stocks have 

 failed to give such aberrant viability. 



Another explanation, that has been more recently applied to 

 particular instances in which a character ordinarily of excellent 

 viability has not appeared in the expected proportion, in that 

 a lethal gene is present. Thus, an autosomal lethal in the 

 second chromosome and quite far to the right of vestigial (i.e., 

 close to speck) would give results roughly comparable to those 

 observed. The difficulty with such an explanation in this case 

 is that the uniform results given by all the cultures would re- 

 quire the lethal to be present in nearly all the individuals— a 

 frequency entirely out of the question both from a priori con- 

 siderations and from the results of subsequent tests made with 

 these stocks. Such lethals as have been found in the vestigial 

 stock (by L. J. Cole and by students at Columbia) should not 

 give results like those observed. 



