244 GENETIC STUDIES ON THE SILKWORM 
22) I believe mosaics are produced by mutations, either major or minor, 
occurring in the segmenting cells in different stages of embryonal develop- 
ment. By "mutation" I mean assumed sudden check of physiological 
functions of a gene or genes, or a sudden revival of them in the egg-cells. 
23) Mosaic abnormality in the silkworm are not only known with regard 
to various larval patterns (striped, moricaud, normal, plain, quail, zebra, 
multilunar), body colour (opaque and oily) and sax, but even size mosaic has 
been observed, though only once. 
24) Mosaics appeared in hybrids as well as in pure breeds, but they 
are more frequent in the former. 
