OTHER THEORIES OF SPECIES-FORMING. 



299 



''In these variously-fed worms there exists a very definite and 

 constant relation between amount of food and size as indicated by 

 weight, the starveling individuals being consistently smaller than 

 the well-nourished, the lingering effects of this dwarfing being 

 handed down even unto the third generation, although the progeny 

 of the famine generation be fed the optimum amount of food ; in 

 case the diminished nourishment is imposed upon three, or even 

 two successive generations, there is produced a diminutive, but 

 still fertile, race of Lilliputian 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 advan- 

 tageous 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 examination 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 

 t>y the modes of frequency polygons erected to include all the 

 individual weights for each lot at spinning time. 



''We find that control lot I, consisting of normally-fed indi- 

 viduals of normal ancestry, holds first rank in weight, as was to be 

 expected. Second comes lot 5. whose grandparents experienced a 

 famine but whose parents as well as themselves 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 



