K. ToYAMA 367 



IV. Crossing of various Breeds or Variants possessing 



DIFFERENT EGG-CHARACTERISTICS. 



Series 1. Crosses between the wild (Theophila mandarina, M.) and 

 the domesticated {Bombyx mori, L.) mulberry silk-worms. 



The egg of the wild mulberry silk-worm (Fig. 10, a, b) is deposited 

 in a small group on stems or twigs of the mulberry tree. When newly 

 laid, it is a straw yellow (Fig. 10, b) which with the formation of the 

 blastoderm gradually assumes a brownish tint and at last turns greenish 

 grey (Fig. 10, a). The shape is nearly the same as those of cultivated 

 ones, while the size is little smaller than the latter. The shell is straw 

 yellow and translucent. 



The egg of the domesticated silk-worm used in this series of 

 experiments is light greenish white when newly oviposited. It gradually 

 assumes, as in the wild form, a brownish tint and turns brownish slate 

 with some shade of purple or pink, i.e. it assumes the normal colour of 

 Japanese silk-worm eggs (Figs. 1, 3, 11). The shell is nearly white, 

 rarely faintly shaded with a greenish, brownish, or other tint. 



In the spring of 1905, five wild female moths were mated with 

 domesticated males (tetravoltine Tobuhime). They deposited, with no 

 exception, eggs whose characteristics are the same as those of pure wild 

 ones in every respect, such as colour, shape, size and brood character 

 (voltinism). On comparing them with those laid by pure wild parents, 

 we were not able to find any difference at all. 



Eleven reversed matings (uni-, di-, and tetravoltine females with 

 wild males) gave, on the contrary, eggs which are similar in shape, 

 colour and voltinism to those of pure domesticated ones (Fig. 11). 

 Even the eye of experienced breeders is not able to distinguish the 

 cross-bred eggs from those laid by maternal pure breeds. 



Other five batches derived from divoltine females in the spring 

 brood mated with wild males are all divoltine white in colour, and thus 

 the order of inheritance is entirely maternal, no paternal influence being 

 observed in those reciprocal matings. 



The worms which emerged from the reciprocal F-^ eggs were reared 

 in the summer of the same year. Moths derived from the eggs laid by 

 the wild female matings (five matings) gave 56 batches of eggs, all 



