K. ToYAMA 353 



II. Origin of the Characteristics above enumerated. 



The egg consists of the shell, vitelline membrane, serosa and yolk, 

 and each of them is coloured or shaded with certain tints or pigments, 

 except the vitelline membrane which mostl}' remains colourless in nearly 

 all breeds. 



The shell is usually translucent and is slightly tinted with certain 

 colours. In Japanese breeds it is usually white or slightly shaded with 

 brown, flesh-colour, green, or dirty- white or some other tint. That of 

 some Japanese green, Chinese or European breeds is coloured yellowish 

 green or pale green. The colour of the eggs is consequently more or 

 less influenced by the colour of the shell. As to the shape, it is chiefly 

 determined by the characteristics of the shell, which is derived from the 

 epithelium of the oviduct. 



The cause of the egg-colour is, however, mostly due to the pigments 

 deposited in the serosa which are seen through the shell. 



The colour of the yolk plays a certain part in the production of the 

 egg-colour only in the case where the formation of the dark pigments in 

 the serosa does not take place, i.e. in newly laid eggs or those oviposited 

 by the spring brood of di-, tetra-, or multivoltine breeds. 



The object of the present series of experiments is to know what 

 influence, if any, these variants have upon the trend of heredity in 

 their offspring. As to the origin of these variants we are quite ignorant 

 whether they are produced by mutation or by hybrid mutation or some 

 other causes which are yet unknown to us. We only know that they 

 are seldom found among eggs laid by the normal-egged breeds generally 

 reared in Japan. 



III. Results of Line Breeding of certain Variants. 



Series 1. The Reddish-Brown Eggs (Figs. 1, 2). 



In the winter of 1907, Mr K. Ishivata, one of the famous silk- worm 

 breeders in the district of Fukushima in Japan, kindly offered me some 

 normal (Fig. 1) and brown (Fig. 2) egg batches' laid by a divoltine 

 white breed called " Shinkawachi," and said that both of them, even 

 when inbred, gave the antagonistic characteristics in the offspring and 

 thus it was very difiicalt to establish them as constant forms. 



' All through this paper, the word "batch " represents the total eggs laid by a moth. 



