MISCELLANEOUS 53 



tion equals the sum of the parent races, while in still others it is midway 

 between the percentage of the parent races. 



All of these data would seem to indicate unmistakably that double 

 cocooning is a heritable condition and not a purely ontogenetic one. 

 They would also indicate that this condition can be fostered or modified 

 by selection and thus made into a racial character. 



My own work on double cocooning resolves itself practically into 

 an attempt to foster (or to test) this habit by selection. Experiments 

 were begun in 1902 by mating together a male and female, both of 

 which had issued from the same double cocoon. All the eggs of this 

 mating hatched prematurely except two, the larvae from which were 

 reared and spun single cocoons. The moths issuing from both these 

 cocoons were both females and were mated one with a male from a 

 double cocoon and one with a male from a single cocoon. 



From the general 1903 rearings I collected 9 double cocoons (6 

 yellows, 3 whites). They varied considerably in shape, the extremes 

 being, respectively, round, elliptical and elongate spindle shaped. In 

 no case was a mixed yellow and white double cocoon found. With the 

 moths from these 9 double cocoons together with some moths from 

 single cocoons, 14 pure and cross matings (on a basis of cocooning 

 habit) were made so as to bring together male moths from double with 

 female moths from double, male moths from single with females from 

 double, and males from double with females from single. Also in 

 mating males and females from double cocoons together care was 

 taken to cross the colors, i. e., a moth from a yellow double would be 

 mated with a moth from a white double. Also pure matings were 

 made in this color respect, thus yellow double with yellow double and 

 white double with white double. 



The results of the rearings of the various lots of eggs derived from 

 these matings were as follows : 



From 5 lots of eggs with both parents from double cocoons only 

 two double cocoons were obtained, three of these matings producing 

 no double cocoons at all. (These lots were greatly cut down so that 

 comparatively few larvae were allowed to spin up, but there was plainly 

 no inherited tendency to produce doubles.) 



From the matings in which one parent was from a double and the 

 other from a single, 9 matings altogether, only 2 double cocoons were 

 obtained, a single double cocoon appearing in each of two of the lots. 

 (These lots also were very small.) 



From a mating made between a moth from a double and a moth 



