236 Heredity and Eugenics 



parallel bands. A double-striped condition in place of a 

 single stripe. 



Many of the mid-types exhibited the same modifica- 

 tion to a lesser degree, especially the break in the band. 

 A female of this double-striped character was mated with 

 an extracted male undecimlineata (a brother) , and when in- 

 bred there were obtained in the next generation adults with 

 the elytral stripe single, the elytral stripes single and broken, 

 double, double and broken. From these it has been pos- 

 sible, by a process of analysis, to develop the following stable 

 combination : a type in which the larva is white with large 

 black spots upon the back like the larva of signaticollis , but 

 with the ground color white, and with the elytral stripes 

 double in the adult; the same type with the stripes double 

 and broken, and the same type but with the ramous and 

 first costal stripes also broken. Third, the same type of 

 larvae, but with all of the stripes broken. The elytral 

 stripes are extremely invariable and most difficult of modi- 

 fication, but this example shows clearly that by combining 

 in the process of hybridization characters accentuated by 

 selection — and it will probably be true of characters accen- 

 tuated in any other way — that there is a definite increase 

 in the modification of characters and that they are rendered 

 stable in the constitution of the gamete and might easily 

 take part in the formation of species. Figs. "jGA-G show 

 some of the types thus far obtained from an evolution 

 movement initiated by the process described. 



In these experiments the modifications are in no wise 

 due to the influence of external factors; in fact, they were 

 carried out under relatively constant conditions, nor is it 

 conceivable that external factors could be productive of such 

 a result. What it is that has brought about these modifica- 



