Toyama, On certain characteristics of the Silk-worm etc. li()| 



and its surface is convex when newly laid but after a few days it 

 becomes depressed in the middle, thus producing the characteristic 

 form which is familiar to us. As in the colour, there are many 

 variants, the one with which we made our experiments being a 

 spindle-shaped variant derived from a normal-egged breed. 



As the egg consists of the shell, vitelline membrane, serosa 

 and yolk, each of which is coloured or shaded with certain tints 

 or pigments, except the vitelline membrane, the colour of the egg 

 is formed by the combination of those colours. In the case of the 

 variants enumerated above, the colour is mostly influenced by the 

 serosa, in which plenty of pigments are deposited, the colour of 

 the shell and yolk playing a very small part in forming the colour 

 of the egg, since most shells are white or only slightly shaded, 

 except that of the green breed in which we find deep green coloured 

 shells. 



In the newly laid egg, the colour of the yolk plays an impor- 

 tant part in forming the colour of the egg. 



As to the shape, the shell is the chief factor in determining 

 it. Those characteristics such as w 7 hitish grey eggs and spindle- 

 shaped eggs belong to this category. 



Now, then, let us quote here the results of line breeding on 

 breeds possessing certain special egg characteristics. 



Serie I. 

 The liulit l)rown egg. 



In the winter of 1907, w T e obtained certain batches of eggs, 

 some of them being light brown and the others normal brownish 

 slate. Both of them were derived from a divoltine white called 

 "Shinkawachi". Each of them, when inbred, gave the antagonistic 

 characteristic in the following order: 

 Parent Eggs Normal coloured eggs 



F! (Brown -f- Normal) 



F 2 All divoltine White 7 ) All divoltine White 



F 3 N (10) + B (30) + M (30) B (10) + N (10) + M (18) 



F 4 All W B(14) + N(28) -f M (16) 



F 5 All B (04) B (1) + N (6) + W (48) 



F 6 ^AH~ 'N (6) + W ' 



F 7 All B (572) X(25) + w(4K 



B = brown batch; N = normal; W = divoltine white; M = mixed batch of 



brown and normal. 



7) In di-, tetra- or multivoltine breeds, the eggs laid by the spring brood 

 generally do not develope any dark pigments in the serosa and therefore they remain 

 pale white in colour until the embryo is developed. This is a normal characteristic 

 of these breeds. 



