BOARMIDyE-SELENIA. 87 



In the year 1887, Mr. Francis Galton, in the course of some 

 commnuications to the Entomological Society of London, 

 made suggestions as to the desirability of so breeding insects 

 as to establish o. pedigree with definite objects. His wish was 

 to start from the brood of a single pair of moths, and to trace 

 the change of some one characteristic — say of the wing-length 

 — during many successive generations, down three parallel, 

 but well-contrasted, lines of descent ; the broods being 

 reared all along out of doors, and under healthy and per- 

 fectly identical conditions. One line of descent to be pro- 

 duced by selecting and mating one or more pairs of the 

 largest-winged males and females that are to be found in the 

 brood of the original pair; out of their progeny a similar 

 pair, and thus onward, to obtain the largest producible size. 

 A similar course to be taken "with the smallest pair and its 

 smallest progeny ; and as a third series, pairs of medium 

 size ; and this to be continued for at least six generations. 

 For this purpose it was desirable to find a species easy to 

 rear, naturalh^ somewhat variable in size, and also double- 

 brooded, that the time necessarily occupied might be as short 

 as possible. The present species appearing to be one of the 

 most desirable and suitable in these respects, the task was 

 undertaken by Mr. Frederic Merrifield, of Brighton, with 

 friends ; eggs were obtained, the resulting larvo3 tended by 

 him with the utmost care and entire success, and the experi- 

 ment fairly tried during a nuuiber of generations. But 

 Nature stepped in with her (unexpected) limitations. By 

 care that interbreeding should not be too close, by repeated 

 change of food-plants, and of other conditions, it was found 

 practicable to continue all the races almost indefinitely ; but 

 in the cases of selection of largest and smallest specimens, 

 breeding by selection still larger, and still smaller, it was 

 found that, when the sizes began to go much beyond the 

 range of the species in nature, it was impossible to continue 

 the experiment, the numbers of specimens in a generation 

 becoming so small that there was not scope for the necessary 



