244 Heredity and Eugenics 



In Fig. 79 are brought together in diagrammatic form the data 

 and general history of cultures where both light and dark forms were 

 produced and further subjected to experiment. The black polygons 

 represent the selected groups of parents, the ruled polygons, the 

 offspring. The appearance of "mutants" beyond the normal range 



of variability is indicated by the small white polygons The 



series is a complex one, involving processes other than artificial 

 selection and introducing factors of interest which are the key to 

 further experimental study. At present only that portion directly 

 concerned with selection or selective processes need be considered. 



In the first, or parent, generation I selected 6 copulating pairs of 

 beetles from the hibernating population, and kept them and their 

 progeny in natural conditions. From the 6 pairs were obtained in 

 the second generation 1,320 mature beetles, and from these, two 

 groups of copulating pairs of 10 each (A and B) were selected and 

 reared in the third generation, but showed no modifications as the 

 result of selection. These hibernated, and selections from each lot 

 were reared in the fourth generation, but showed no modification. 

 I now felt sure that the material was pure, that is, normal, and carried 

 no tendencies to appear in divergent extreme variations. Accord- 

 ingly, from the two series selection was made of as nearly modal 

 individuals as possible, and the two selected lots were mixed and 

 divided into two lots of 10 pairs each (C) and (D). These were 

 placed, as soon as possible after emerging, in surroundings produc- 

 tive of dark and light conditions of coloration, and allowed to breed, 

 producing in the fifth generation two distinct lots of descendants, 

 one light, the other dark. These hibernated, and after emerging 

 in the following spring were allowed to breed, when it was found that 

 out of 50 mated pairs 31, or 62 per cent, were able to transmit their 

 particular variations in full strength, a huge increase over that 

 found in selections from nature. From each group 5 pairs were 

 selected as the parents of the sixth generation. These gave, as was 

 expected, distinct lots of individuals more melanic and more albinic 

 than their parents, and each also produced individuals differing in 

 many respects from the parent stock, and beyond the usual range of 

 variability. In the five following generations the same thing was 

 repeated, as may be seen from Fig. 79; that is, from each group of 



4 



