8o 



INHERITANCE IN SILKWORMS^ I 



silkworms whose moths, as regards wing expanse, might join the ranks of the 

 micro-Lepidoptera almost unremarked. 



In illustration may be quoted the typical or modal larval weights for each 

 of the lots of 1903 at the time of readiness to spin, which marks the completion 

 of the feeding and is, therefore, an advantageous point for a summary of the 

 results of the three years' experimental feeding. 



The history of the eight lots referred to may be gathered from an examina- 

 tion of the accompanying table, in which "O" means optimum amount of food and 

 "S" means short rations. The column to the right indicates the relative rank of 

 the various lots as judged by the modes of frequency polygons erected to include 

 all the individual weights for each lot at spinning time. 



We find that control lot 1, consisting of normally fed individuals of normal 

 ancestry, holds first rank in weight, as was to be expected. Second comes lot S, 

 whose grandparents experienced a famine but whose parents as well as them- 

 selves enjoyed years of plenty. Lots 2 and 3 have likewise had one ancestral 

 generation on short rations, and the fact that they are lighter in weight than 

 lot 5 illustrates a general rule which obtains throughout the entire company of 

 experimental worms, namely, that the effects of famine grow less evident the 

 further removed the individuals are from its occurrence in their ancestral history. 

 Thus lot 5 is two generations removed from the famine of 1901, while lot 3 has 

 had but one generation in which to recover its ancestral loss. Lot 2, which has 

 had a total of but one famine year — the current year — nevertheless ranks below 

 lot 7, which has had two famine years in its ancestry succeeded by plenty during 

 the current year. Lot 2 also ranks below lot 6, a fact which appears strange, 

 considering that lot 6 has suffered two generations of famine, including the 

 current year, which is the only famine year experienced by lot 2. In explanation 

 of this anomalous condition it is suggested that possibly the larvae of lot 6 were 

 better fitted for enduring the making the best of hard conditions than were the 

 individuals of lot 2, the ancestors of the former lot having been selected two 

 years ago on a food-scarcity basis. This suggestion gathers support from an 

 inspection of the mortality notes, from which it appears that the number of 



