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Y. TANAKA. 
we speak of “yellow silkworms”, therefore, we mean yellow-legged larvae, 
and at the same time yellow-cocoon spinners. It must be noted, however, 
that the intensity of the yellow leg-colour is by no means proportional to 
that of the cocoon colour. In my experiments it was found that some larvae 
with so faintly yellowish legs that they were mistaken for white-legged ones 
spun intensely yellow-coloured cocoons, while some of the worms which had 
deep-yellow. legs produced merely creamy or salmon-yellow cocoons. 
2) I. Inhibitor. 
This factor totally suppresses the development of yellow colour. The 
inhibitor is contained by the so-called dominant whites in the European 
races, for instance Bagdad , Blanc pays, Blanc des Alpes, etc., the constitution 
of the homozygous forms of them being II YY or Hyy. The larva which 
involves this factor is always white-blooded, but the cocoon is often shaded 
with light greenish colour. (Experiments : Coutagne, Kellogg.) 
3) i. Absence of inhibitor. 
The inhibitor is always absent from vellow-cocooners and the so-called 
recessive whites. 
4) y. Absence of yellow ; white cocoon, 
A recessive white results from the abienee of both the factors for yellow 
and its inhibitor ; it may be expressed as iiyy. The larva of recessive white 
is white-blooded, and spins pure white cocoon. All oriental whites, as yet 
known fall into this category. (Experiments : Toyama, The Author.) 
Experimental Results of Previous Authors in 
the Light of the Presence and Absence Hypothesis. 
1) The results of the author. 
The experimental results of the author are all interpretable on the 
basis of his postulated factors described above. The more important of 
these results are described in detail in a separate paper. 
2) The results of Kellogg and Quajat. 
