294 liEPIDOPTERA. 



"He attributed the enormous loss of silk-vrorms by mus- 

 cardiue and other diseases, and the consequent diminution 

 of the crop of silk, to the combined effects of bad and scanty 

 food, want of sufficient light and ventilation, too high a tem- 

 perature, and constant interbreeding for centuries of a debili- 

 tated stock. He asserted that there was no such thing now in 

 existence as a perfectly healthy domesticated stock of silk-> 

 worms ; and moreover, tliat it was useless to seek for healthy 

 seed, for whether in Europe, Persia, India or China, the worm& 

 were all equally degenerated, or, if there were a difterence at 

 all, it was in favor of the European race. He had for several 

 years been experimenting on Bombyx mori, with a view, if 

 possible, to reclaim the worms, to restore to them a healthy 

 constitution and to induce them to revert from their present 

 artificial and moribund condition to one of vigor and perma- 

 nent health. The occasional occurrence in a brood of one or 

 more dark grey or blackish-brindled worms — the 'vers tigres' 

 or 'vers zebres' of the French — contrasting strongly with 

 the pale sickly hue of the majority, must have been noticed by 

 all who have had experience in rearing silk-worms ; such occur- 

 rences have been always spoken of as indicating varieties aris- 

 ing from domestication. The author had endeavored, by a series 

 of experiments, to ascertain the cause of this phenomenon, his 

 conviction being, either that the species had at some time or 

 other been crossed by another of different colors, and that Na- 

 ture, as sooner or later she always would do, was making an 

 effort to separate them, or that the original color of the worm 

 had been dark, and an effort was being made to revert from a 

 sickly condition to the original healthy starting point. He ac- 

 cordingly picked out all the dark colored worms and reared 

 them separately, allowing the moths to couple only inter se, and 

 the same with the white worms. In the following spring the one 

 batch of eggs produced nearly all dark brindled worms, whilst 

 the other batch produced white worms, sparingly interspersed 

 with an occasional dark one ; these latter were removed into a 

 dark batch, which was also weeded of its pale worms. In the 

 third year the worms were still darker than before, and were 

 always larger and more vigorous than the pale ones, giving 

 larger and better stuffed cocoons. He finally succeeded in 



