THE DETERMINATION OF DOMINANCE. 29 1 



L. signaticollis . There are no other simple differences between 

 the three species that could be readily utilized in experiments 

 of this kind, but the characters used are sharp and striking, and 

 satisfy in every respect the conditions demanded by Mendelian 

 hypotheses. 



Fig. 2. L. undscimlineata Stal. (A) Adult. Showing on the elytra the pres- 

 ence of longitudinal pigmented bands which are bordered by rows of punctations 

 as in L. signaticollis. The pigmented bands may be considered the positive half 

 of a Mendelian allelomorph, so that when the two species are crossed we are following 

 all of the Mendelian qualifications in crossing the presence and absence ot the same 

 character. {B) Full-grown larva, showing the characteristic color pattern in this 

 stage. The ground color is pearly white. (C) Second stage larva, showing the 

 characteristic color pattern. The ground color is also pearly white. 



The elytral stripes of L. diver sa and L. undecimlineata repre- 

 sent the present or positive character, and the lack of stripes in 

 L. signaticollis the absence or negative factor of an allelomorphic 

 pair, the yellow hypodermal color one member and the white 

 the other of an allelomorphic pair: yl = ( + ) wh = ( — ); the 

 dorsal spots the presence ( + ) and their absence the absence 

 a( — ) of another pair of allelomorphs — when we view the char- 

 acters from the present Neo-Mendelian standpoint. 



A further reason for choosing this material for this investigation 

 is the fact that when crossed it often gives most perfect Mendelian 

 results, and in some cases perfect ratios of 1:2:1 are obtained in 

 the second hybrid generation, while other crosses, brothers and 

 sisters of the same material, did not give the same, but on 

 the contrary, quite different results. For some time I was at 

 a loss to understand the reason for this anomalous condition. 

 No amount of crossing or investigation succeeded in disclosing 



