1 86 W. E. Castle 



then dies. These eggs either hatch and produce a second genera- 

 tion of moths the same season (bivoltinism) or else hold over to 

 the next spring before hatching (univoltinism). All the eggs laid by 

 the same moth behave in the same way, regardless of the charac- 

 ter of the male that fertilized the eggs, as well as of the character 

 of the moths which are to develop from the eggs. Thus a univol- 

 tin mother may produce both univoltm and bi vol tin daughters, 

 but neither sort will hatch from the egg before the following spring. 

 And the eggs of a bivoltin (spring generation) mother will all 

 hatch the same summer, regardless of whether her female descen- 

 dants are to function as bivoltin or univoltin egg-layers. 



It therefore becomes somewhat difficult to trace the decent of 

 the contrasted race characters. And to free either condition from 

 the other, when they have once been crossed, is doubly difficult 



because the germinal constitution of the individual can be de- 

 cs 



tected neither in the adult males, nor in the second (summer) 

 generation of females. 



Plant-breeders have encountered puzzling conditions of a some- 

 what similar nature, but happilv have found a complete and 

 simple explanation of them. This explanation, I believe, will 

 apply with modifications to the case under discussion. 



In maize, red color of the seed-coat (or pericarp) is a Men- 

 delian dominant to its absence (white seed-coat), but the red 

 color of the seed-coat is of purely maternal origin, and has no re- 

 lation to the transmission of red or its opposite by the embryo 

 lying within the seed-coat. If the plant of red-seeded maize is 

 pollinated with pollen from a white-seeded variety, red seed is 

 produced though the contained embryos are heterozygous, red 

 (white). Now if this seed is planted, again only red seed will be 

 produced, the heterozygous mother plants showing only the domi- 

 nant character in the ears which they bear. But the embryos 

 contained within the second crop of seed will be of three sorts in 

 accordance with Mendel's law, viz: iRR, 2RW, and iWW. 

 Plants raised from embryos of the first two sorts will bear red 

 ears, but a plant raised from a WW embryo will bear white ears, 

 even though the seed-coat which covered that embryo was red. 

 And if such WW plants are self-pollinated or pollinated ttiterse, 

 no red ears will be cbtained thereafter, as shown by Locke ('06). 



