Modification of Germinal Conslitution of Organisms 233 



black pigment at the bottom of each. By a process of 

 hybridization and extraction it is possible to obtain a race 

 of signaticoUis which, if found in nature, would be regarded 

 as a distinct species; and when it occurs in experiment it 

 behaves with the same sharp alternative distinctness of any 

 natural species. 



If a female of L. imdccimUncata, which has the larval 

 ground color white without any black spots on the back, 

 and with one row of black spots surrounding the spiracles 

 in the adult larvae and the impressed punctations very 

 regular in pattern with the rows closely parallel, is crossed 

 with a male of L. signaticoUis, the F^ generation gives two 

 t}'pes of larvae (yb) and {whs), in the proportion of 1:1. 

 From the {y\s) larvae will come a tj-pe intermediate between 

 the two, and this type, when inbred, gives in the second 

 hybrid generation four t}'pes of full-grown larvae (ivhs), 

 iwJiS), iyVS), and {y\s). From the {wlis) larvae in the 

 second generation are obtained three classes of adults : like 

 the female parent, L. iindccimlineata, like the male parent, 

 L. signaticoUis, and intermediate between the two. 



If, now, a cross be made between these extracted F, un- 

 decimlineata t}'pes with the extracted F^ signaticoUis type, 

 we get in Fj mature larvae which are iwhS), and these 

 give mid-type adults in which the elytral punctations are 

 arranged in closely parallel rows like the widccimlineata 

 t>'pe. These, when inbred, give in F^ larvae which 

 are (wJiS) like the undccimlineata t^'pe, and these larvae 

 give three tj-pes of adults: like the undccimlineata t}j>e, a 

 mid-t>'pe, and like the signaticoUis t>pe. 



The signaticoUis type which comes out of these crosses 

 is the modified signaticoUis type, and these, when inbred, 

 have a hfe cycle shorter than is normal to signaticoUis. 



