ECONOMIC ASPECTS OF STUDIES IN SILK- 

 WORM INHERITANCE. 



In their recent comprehensive treatise (Traite sur le Ver a Soie du 

 Murier et sur le Murier, 1906) on commercial silkworm rearing, Maillot 

 and Lambert of the principal government experimental silk culture sta- 

 tion of France (at Montpellier) discuss the effects and advantages of 

 the crossing of silkworm races and of individuals of the same race 

 reared in separated localities. Their statements are based on the 

 experience of long years of rearing, observation and selection. 



First, they find that crossing, even between moths of closely allied 

 races, produces individuals "more vigorous, more productive, more 

 fecund." 



Then they utter certain generalizations concerning the results to be 

 expected from certain crossings. For example: "if one mate a male 

 moth of a race that lays adherent eggs with a female moth of a race 

 laying non-adherent eggs there will be more chances that the eggs pro- 

 duced by the hybrid young will be non-adherent ; but in the reciprocal 

 crossing [i. e. male of non-adherent eggs with female with adherent] 

 the contrary will most often occur." 



Also "if one crosses a race with large, cylindrical, yellow cocoons 

 and worms large and of slow growth, with a race with small, oval, 

 white cocoons and worms smaller and of rapid development, one will 

 have in the first generation both yellow and white cocoons, of each 

 type, sometimes in numbers almost equal, sometimes many more of 

 one type than of the other ; the worms will differ from worm to worm : 

 some will be of the type of the male race, large and long lived ; others 

 will be of the type of the female race, small and short lived ; others yet 

 will show the characters of both races. Thus in a crossing of 

 worms with white skin with worms of black skin one will find some- 

 times individuals which have half of the body with the skin black the 

 other half with the skin white. The separating line being the median 

 longitudinal one. 



"In the crossings between races of differently colored cocoons the 

 most advantageous one, that which offers the best guarantee in the 

 matter of the homogenousness of the cocoons produced, both as to 

 quality and quantity, will be a crossing of a male of yellow 

 cocoon with a female of white cocoon. One can affirm nothing with 

 certainty concerning the inheritance of the tendency which is shown 



