Ebactions and Products in Inteespbcipio Ceosses 141 



tion to the ratio of 1 : 3 : 1, in individual experiments shows wide ranges there- 

 from, and these are in close correlation with the differences present in the dur- 

 ation of the ranging conditions used ia the medium. The range shows oscilla- 

 tions towards both of the extreme or pure-breeding conditions, and in nature 

 the same cross might well be productive of different results and sequences of 

 consequences in the local fauna as the product of the conditions surrounding 

 the initial cross. 



The last complication in this series of experiments that need be mentioned 

 here is the crossing of these two species, under conditions of high temperature 

 and moisture with little evaporation and air-movement. The foUowiag com- 

 plex of conditions with these materials has given the result that the progeny in 

 Fi are all alike and of the undecimlineata type, breed true, and appear as if the 

 other parent had gone from sight. This result I have thus far obtained only 

 when the female parent was undecimlineata, in 12 trials out of 19, giving in Pj 

 317 adults. The converse of this has not been produced when signaticollis is 

 the female parent. These crosses have been tested in three series, and by 

 the tests that were applied to the other Pj pure-breeding types are shown to 

 be in all respects heterozygous and of the same composition and apparent ease 

 of dissociation; likewise they have the same slow-breeding reactions that are 

 present in the other strains of the same origin. Aside from this aspect these 

 last experiments are without much interest. 



The intercrossing of these two species under different conditions shows the 

 production in experiment, and the same no doubt is true in nature of 10 pure- 

 breeding strains, or races that are different, so that in nature they might easily 

 be described as species. By pure-breeding I mean only the usual application of 

 the term, the production of progeny that are the duplicate of the parents, a 

 term and description that are not of much significance at present. The 10 pure- 

 breeding lines show two groups: (1) a group of 8 that are liomozygous in 

 action and in constitution, and (3) a group of two that are homozygous in 

 action, but heterozygous in constitution. In appearance these are as follows : 



(a) Homozygous in constitution and in action, always derived as F^ extractives. 



L. signaticollis (a) signaticollis in all respects, with yellow-spotted 



larvae. 

 L. signaticollis (&) signaticollis with white larvae, spotted with black in 



third stage. 

 L. signaticollis (c) signaticollis with yellow larvae, not spotted in the 



third stage. 

 L. signaticollis (d) signaticollis with white larvae, not spotted in the 



third stage. 

 L. undecimlineata (a) wndecimZweaf a with white larvae not spotted. 

 L. undecimlineata (6) undecimlineata with larvae white spotted with 



black. 

 L. undecimlineata (c) undecimlineata with larvae yellow spotted with 



black. 

 L. undecimlineata (d) undecimlineata with larvaa yellow spotted with 



black. 



(b) Homozygous in action, heterozygous in constitution and always derived 



in "FT 



L. undecimlineata (e) undecimlineata with white larvae not spotted. 

 L. signaticollis (e) signaticollis with yellow larvae spotted. 



