MENDELIAN FATORS IN THE SILKWORMS. 
97 
shades or totally disappear »from the full-grown larvae. The plain silkworms 
being one of the most common strains, it is found in almost all European and 
Asiatic races. 
The plain is of course recessive to all marked characters. ( Experi- 
ments : Toyama, Kellogg.) 
Equipotency and Incomplete Dominance of Marking Characters. 
In the crosses moricaud x zebra, Coutagne obtained a new type of 
marking, i. e. morieaud-zebra, in which the moricaud and the zebra-pattern 
simultaneously appeared with equal strength. According to Toyama an 
apparent combination of two distinct markings also takes place between poly- 
lunar pattern and the striped, moricaud or zebra. These curious phenomena 
are perhaps due to equivalency of the dominating power of two characters 
for which an individual is heterozygous. 
On the other hand incomplete dominancy of marking characters is also 
remarkable in heterozygous striped or moricaud. The heterozygous forms 
of these marked strains are always lighter-coloured than the homozygous 
individuals. Thus we can distinguish, without great difficulty, the SSzzmm- 
lin larvae from the Sszzmmnn, and the sszzMMnn individuals from the 
sszzMmnn form. 
II) Factors for Cocoon Colours. 
1) Y. Yellow cocoon. 
By the term “yellow” we mean all coloured cocoons, except green ones, 
varying from creamy to golden yellow. A constant colour-correlation between 
cocoon and blood color is a well known fact ; the yellow-cocoon spinners are 
always yellow-blooded, while the white cocooners are white-(colourless) blood- 
ed. The blood colour is visible through the euticular coat of the larva, 
especially on the ventral side of the body and on the abdominal legs. When 
