120 Isabel McCracken. 



The question arises, "How do these extremes of color and pattern 

 behave in heredity ?" Having no known pure bred stock to begin 

 with, my first attempt was to breed out by selection the alternative 

 color from each of the two extreme lines. Succeeding in this, 

 I hoped to have on hand material for testing the validity of Men- 

 del's laws of "dominance and segregation" for this species. In 

 pursuance of this the following breeding experiments were devised 

 and carried out, and the results recorded in detail. In the suc- 

 ceeding tables summaries only are given. 



III. METHOD OF EXPERIMENTATION AND RESULTS. 



Experiment i. To determine relation of first generation from 

 laboratory reared adults to the color types S and B. (Table I.) 



Experiment 2. To determine relation of second generation 

 bred from similars to color types S and B. (Tables II and III.) 



Experiment 3. To determine relation of individuals bred for 

 two generations from similars to the color types S and B. (Tables 

 IV and V.) 



Experiment 4. To determine relation of offspring of extremes, 

 having on each side pure heredity for at least a generation to the 

 color types S and B. (Tables VI, VII and VIII.) 



Experiment 5. To determine in what generation from mixed 

 parentage the alternative characters breed pure. (Tables IX 

 andX.) 



Experiment I. The generation with which this work was 

 begun was collected in last larval instar from willow trees in a 

 certain locality in the neighborhood of Stanford. These were 

 caged in the laboratory, and thereafter fed upon poplar and 

 willow leaves until pupation. As soon after emerging as the 

 wing color was established, namely, in about an hour, the adults 

 were placed in one of four breeding cages as follows: 



Cage I. Black cJ^'s and black v 's only. 



Cage 2. Spotted c?'s and spotted 9 's only. 



Cage 3. Black c?'s and spotted 9 's only. 



Cage 4. Spotted d^'s and black 9 's only. 



Sex was determined by size. Individuals not exhibiting 

 extremes of size, namely, individuals not easily distinguished as to 



