352 Maternal Inheritance and Mendelism 



In my first contribution to the study of hybridology of insects 

 published in 1906 (10), it was shown that certain colour-characteristics 

 of the egg of the Siamese silk-worm follow Mendel's law of heredity. 

 Thanks to the kind suggestion of Prof. Bateson of London, we again 

 undertook a similar series of experiments with various breeds of the 

 silk-worm. Some of the results obtained during the last five years 

 which seem to us to be not without interest to students of heredity will 

 be described in the following pages. 



I, Certain Egg-characteristics of the Silk-worm. 



Before going further, we shall first enumerate certain egg-character- 

 istics which are the subject of the present paper. 



Colour. The ordinary colour of the Japanese silk-worm eggs is 

 a light greenish white when newly laid. With the formation of the 

 blastoderm, the egg gradually assumes a brownish tint which at last 

 turns into brownish slate shaded with some light pink or purple 

 (Figs. 1, 3, 11). There may be found, however, many variants, some 

 rather deeper, some lighter, and some with different shades. Now and 

 again it happens that some eggs characterized by extraordinary variations 

 of colour are found among normal ones, such as reddish brown (Fig. 2), 

 whitish grey (Fig. 4), blue (Fig. 5), greenish slate (Figs. 6, 10, 12), 

 crimson (Fig. 7), orange, greenish white and many others. Most of the 

 eggs deposited by Japanese green breeds are more or less shaded with 

 green. When newly laid, they are yellowish green and are much deeper 

 in colour than those deposited by ordinary white breeds. Most of the 

 Chinese or European breeds come in a similar category. 



Shape. The normal shape of the silk-worm eggs is oval, slightly 

 pointed at one end, where a micropyle is situated (see Figs. 1 — 7). It 

 is a little flattened 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. In this characteristic, as in 

 the case of the colour, we observed many variants, some of them being 

 quite extraordinary, for instance such as spindle-shaped eggs (Fig. 13) 

 or other irregularly shaped ones, etc. which will be discussed minutely 

 afterwards. 



