320 WILLIAM LAWRENCE TOWER. 



the cage and were supplied with food as fast as it was consumed. 

 These gave a very large progeny which appeared to be uni- 

 formly of the dominant types of the first and second genera- 

 tions. Seriation of the material obtained from Generation III. 

 at the end of August, 1909, gave the following results: 



I then mated at random for the parents of Generation IV., 

 one male of B, the only one that could be found alive, three 

 males and three females of C, two males and two females of D, 

 and none of E, they being absent. This material bred at once 

 and gave in the fourth generation a considerable progeny, 

 which were all of the dominant type. 



Material from Generation IV., brought to Chicago in August, 

 1909, placed in hibernation under experimental conditions and 

 brought out to breed in the middle of the winter, has shown that 

 the dominant type is a fixed type, and that it breeds true and does 

 not split in subsequent generations. The only splitting is that 

 which occurs in rare individuals in from two to three per cent, 

 of the progeny, which stand apart from the general population as 

 sports. These cases are practically the reappearance of one or 

 the other of the component characters or combinations thereof 

 that went into the cross, and they do not represent in this ex- 

 periment anything in the way of characters new to the genus or 

 family, as DeVries states to be true of his mutants ; rather, they 

 are simply the characters obtained from the different parents 

 from which this complex has been built up. 



The same combination of material was made in Chicago in 

 1908, and was run through essentially the same procedure as 

 that of the Tucson experiment, with this difference in the result, 

 that at Chicago L. decemlineata completely dominated the culture 

 to the total exclusion, as far as analysis has been able to discover, 

 of the presence of the other parents. 



These experiments in synthesis represent what might happen 

 in a state of nature when species which can hybridize migrate 

 from one place to . another and intercross. No one realizes 



