Dichromatism in Lina Lapponica. 135 



SUMMARY. 



1. No amount of crossing between the two characters in ques- 

 tion accompHshes any disintegration or breaking up of either one. 

 These are absolutely fixed with reference to each other in this 

 species. (Tables I and VIII.) 



2. In the offspring of a cross between the two characters, either 

 both characters, or only one, the spotted, appears. (Tables I and 

 VIII.) (Data on the latter point are insufficient.) 



3. Cross-bred B's, namely, B's appearing in a cross between 

 the two opposing characters, transmit B only to the offspring when 

 similars are bred together. The B character is, therefore, stable, 

 or self-perpetuating in the first generation. (Tables II, IV, VII, 

 IX, XII.) 



4. Cross-bred S's transmit both opposing characters to the 

 offspring, the offspring likewise transmitting both characters, 

 though bred from similar parents. (Tables III, VI, X.) 



5. In the third generation from similar parents, S's appear to 

 breed true. (Table V.) 



While this summary shows no exact parallelism to Mendelian 

 results, it is in accord with Mendelian principles in the following 

 features: 



1. Character S of S X B parentage behaves like a dominant 

 when mated with S. It appears always in greater numbers than 

 character B (with the exception noted in Table I, b) and its broods 

 fall into two categories, i. e., pure broods (each individual being 

 similar to the parents) and mixed broods (broods made up in 

 major part of S, in minor part of B). Its behavior when mated 

 with B must be further noted, I believe, before we can say assuredly 

 that it is a "fully normal Mendelian dominant" in all respects. 



2. Character B behaves like a Mendelian recessive in that from 

 its first appearance (with the exception noted in Table I, h) it 

 reproduces B only. 



3. As to the "segregation" of characters in the germ cell, or 

 "purity of the germ cell," it is evident that only one of the two 

 opposing characters in question is called into activity in the 

 somatic cells capable of expressing it, namely, the cells of the wing 

 covers, and that as far as the experiments extend, individuals in 

 each series appear at once, or eventually, to breed true. 



