ECONOMIC ASPECTS OF STUDIES IN SILKWORM INHERITANCE 63 



Whereas without a knowledge of the Mendelian behavior of cer- 

 tain characteristics it might take many generations of rearing the 

 products of various crossings and selections Maillot and Lambert 

 record that it required 70 generations to establish a certain particular 

 race with this tested knowledge of the behavior in inheritance of 

 specific characters it would be quite possible to fix certain characters 

 in from three to five or six generations. 



Experimental breeding with Mendelian principles in mind will 

 enable the professional silk grower to determine speedily the simple 

 or compound nature of the characteristics of the eggs, larvae, and 

 cocoons ; will enable him to analyze the compound characters into their 

 component simple ones ; will permit him to establish combinations, even 

 very elaborate ones, comparatively rapidly (at least of such character- 

 istics, as show alternative inheritance, that is are Mendelian in be- 

 havior), and will save him much waste of time in purely empirical 

 work. 



His first aim in crossing and selecting will not be the establishment 

 of the desired combination by long-continued miscellaneous trials, but 

 will be the determination of the actual status, as regards behavior in 

 inheritance, of the characteristics he desires to combine and fix. He 

 will determine for each of these characteristics (and two or three 

 generations will tell him) their inheritance habit. Are they unit char- 

 acters ? Are they strictly alternative in inheritance ? Or do they com- 

 bine in the hybrids in particulate (mosaic) manner, or as true blends? 

 Or finally are they so strictly of the nature of simple fluctuations of 

 varying degree or extent about a modal characteristic that they tend 

 strongly to drop back towards this modal type or condition so that only 

 the strictest and most continuous sort of personal selection can main- 

 tain them? 



Among the characters and conditions of eggs, larvae and cocoons 

 forming, in various combinations and degrees of emphasis, the diag- 

 nostic marks of the present silkworm races, characteristics showing all 

 these types or modes of inheritance are included. Color of silk, an 

 important character, behaves usually as a unit character, alternative in 

 inheritance, following, in some degree, the Mendelian principles. Cer- 

 tain colors are then recessive towards others, as white to yellow; 

 salmon to yellow, etc. The relative status of potency (dominancy or 

 recessiveness) can be definitely determined for any two colors, and 

 the silk breeder thus have a knowledge of enormous usefulness in his 

 work of crossing and selecting. Richness in silk (i. e. proportion of 



