FLUCTUATING VARIATIONS AND THEIR INHERITANCE 45 



(Lot M. 49.) W. male mated with M. P. female. Result, i W., 

 loB. P., II M. P., 3 S. P. 



(Lot M. 42.) M. P. male mated with M. P. female. Result, i8 

 W., loB. P., II M. P. 



(Lot M. 118.) S. P. male mated with M. P. female. Result, 5 

 W., iiB. P.,6M. P. 



(Lot M. 58.) M. P. male mated with W. female. Result, 5 W., 

 9 B. P., 10 M. P., I S. P. 



(Lot M. 38.) S. P. male mated with W. female. Result, 4 W., 

 7 B. P., 10 M. P., 5 S. P. (one of these a melanic). 



(Lot M. 45.) S. P. male mated with snowy white female. Re- 

 sult, I W., I B. P., 4 M. P., I S. P. 



(Lot M, 27.) S. P. male mated with a pure W. female. Result, 

 3 W., I B. P., I M. P. 



(Lot M. 52.) S. P. male mated with W. female. Result, 6 B. P., 

 4M. P. 



(Lot M. 51.) S. P. male mated with W. female. Result, 2 W., 

 7 B. P., 3 M. P., 2 S. P. 



(Lot M. 78.) S. P. male mated with S. P. female. Result, 7 

 B. P., 5 M. P., I S. P. and i melanic. 



(Lot M. 113.) S. P. male mated with S. P. female. Result, 2 

 B. P., I M. P., 2 S. P. 



The S. P. pattern is more common among males than females, but 

 is not confined to either sex. 



From these data, the fluctuating and continuous nature of the 

 variation is apparent, and it is equally apparent that there is no alterna- 

 tive character in its inheritance. Rigorous selection would probably 

 be able to produce parents which would throw a larger proportion of 

 S. P. young, and other parents a larger proportion of W. young, but 

 in neither case would this selection probably produce a fixed race. 

 There would simply be produced a condition capable of being main- 

 tained as long as vigorous selection was practised, but only so long. 

 This is the probability indicated by my experiments in attempting to 

 foster the extremes of the pattern variation through several generations 

 by selective matings. 



Wing Venation. 



The variations in the wing venation of a series of silkworm moths 

 constituting a lot of experimental material were studied with a view to 

 seeing whether there are indications of structural degeneration in this 



