VIII] Silkworms 137 



melanic varieties can be given. Of the melanic varieties of 

 Moths which have been tested several are apparently 

 dominant, more or less, to the normal or non-melanic types; 

 but in the black Chrysomelid Beetle, Lina lapponica, inves- 

 tigated by Miss McCracken, the evidence shows plainly 

 that the uniformly black type was recessive"^ to the normal 

 which has black only in the form of spots. The common 

 melanic varieties of the 2 -spot Lady bird (Coccinella bipunc- 

 tata) are probably also recessive to the ordinary red type. 



The experiments of Standfuss interpreted according to 

 the Mendelian system show that the dark variety lugens is 

 dominant to the ordinary fulvous yellow type of Aglia tau 

 (a Saturniid Moth). This case comes up for consideration 

 in some detail with reference to the heredity of Sex {q.v.\ 



In Silkworms a melanic variety of the moth is an im- 

 perfect dominant to the normal, pale-coloured moth, giving 

 a blend-form in F^ (Coutagne, 83). 



As regards the colour of the silk some interesting results 

 have been obtained. Yellow silk was always found by 

 Toyama (268) to be dominant to white, and this result was 

 obtained by Coutagne in certain cases t. For example the 

 yellow race called " Var" was dominant in silk-colour to the 

 white Japanese race used by Toyama and to the white 

 "Bagdad" used by Coutagne; but Coutagne found the same 

 yellow to be recessive to the white of two French races with 

 which he experimented. Presumably this distinction is due 

 to some idiosyncrasy on the part of the whites, analogous to 

 what has been seen in fowls and Primula, but as to this 

 nothing is known. 



In crossing a yellow Siamese race with a white Japanese 

 race, Toyama obtained a resolution -effect in F^, Yellow 

 X white generally gives yellow F^ with 3 yellow : i white in 

 /% ; but in this special case there were two new forms in /%, 

 a pale pinkish yellow, and a greenish white. This latter 

 white could not always be satisfactorily distinguished from 

 the pure whites, so the F^ family has to be taken as 9 : 3 : 4. 



* There is a possible complication in this case. 



t Toyama states that the colour of the silk always corresponds to that 

 of the abdominal legs of the larvae, and consequently it is not necessary 

 to rear all the larvae up to the spinning stage in order to ascertain the 

 colour of their cocoons. 



