96 MASSACHUSETTS HORTICULTURAL SOCIETY. 



Here, again, the selection has resulted in continued gradual 

 deviation in the direction of the selection as if there was a cumula- 

 tive effect. 



The strains selected for high and Ioav oil content, through the 

 same twelve years, gave a gradual increase and decrease in about 

 the same proportion. The evidence thus far obtained does not 

 show whether these strains will be permanent or whether, as in 

 the sugar beet, they will immediately, or soon, revert. It does 

 not show that anything permanent has been added though it does 

 show, apparently, that extremes not present in the original race 

 have been attained. This conclusion would be very important if 

 we could be sure of it, but unfortunately, the number of individuals 

 analyzed in beginning the experiment was only 163, a much too 

 small a number to show the ordinary range of variation. While, 

 therefore, these experiments tend to confirm the belief in a cumula- 

 tive effect of selection, they are as yet inconclusive. 



A series of very interesting experiments has been carried on by 

 Tower in selecting the potato beetle (Leptinotarsa decemlineata) to 

 increase the size and to change the coloration. Careful selection 

 carried on for from 10 to 12 generations, using several characters, 

 has failed to result in carrying the range of variation beyond the 

 normal, and the isolated strains, when allowed to interbreed, with- 

 out selection, revert in a few generations (two or three) back to the 

 normal range. 



DeVries, in selecting corn to increase the number of rows, ob- 

 tained rapid progress at first, but when the selection was discon- 

 tinued the strain reverted almost immediately to the normal t}^e, 

 showing that no permanency had been obtained. 



Castle, in selecting Irish rats to increase and decrease the amount 

 of black color, has obtained evidence favoring the adding up of the 

 • effect of selection, but his published evidence is still inconclusive. 



Other instances might be cited, but it is sufficient to state that all 

 of the evidence now available is inconclusive; and as a whole, 

 rather strongly tends to uphold the conclusions of DeVries. In 

 making this statement, the writer wishes to emphasize that his 

 personal belief is rather toward the selectionist side of the con- 

 troversy. He recognizes, however, that this is more a feeling than 

 otherwise, based on a number of years of practical breeding ex- 

 perience, rather than on carefully planned and executed experiments. 



