THE DETERMINATION OF DOMINANCE. 3 I I 



In 1908 individuals from this location were brought to Chicago 

 and carried as pedigreed cultures in the laboratory. They have 

 shown a complete gametic purity as far as could be determined, 

 and none have been detected which were hybrid in character. 

 In this colony, isolated in its location, through some process or 

 other in hybridization or perhaps by selective factors, signaticolUs 

 has completely subjected and eliminated undecimlineata. Inas- 

 much as L. undecimlineata, when protected from crossing, lives 

 well at Cuernavaca, and the selective action is very low, I 

 am of the opinion that the swamping of undecimlineata is due 

 to some process of hybridization. This opinion is fully justified 

 by experiments conducted in cages which eliminate selective 

 factors. 



L. undecimlineata X L. signaticolUs. 

 Exp. No. C. H. 47.4 Paraiso. 

 This experiment was begun in 1905, when one hundred indi- 

 viduals were taken from the standard colony of L. signaticolUs 

 at Cuernavaca, and, with an equal number of L. undecimlineata, 

 from El Hule, were planted upon a vigorous growth of their food 

 plants in a clearing made in the Foot Hill Rain Forest, in the 

 Paraiso district not far from Ojos de Agua, in the Canton of 

 Zongolica. They were observed to intercross freely, but there 

 was a preponderance of undecimlineata-like forms, with a few 

 intermediates, and only small numbers of the signaticolUs type in 

 the first hybrid generation. The census made of the first hybrid 

 generation was as follows : 



A third generation was produced in late November, and in 

 that generation there were no signaticolUs forms visible; there 

 were only a few of the hybrid intermediate type and these all 

 closely approximated the undecimlineata form. The census ob- 

 tained late in November was 



