THE TECHNOLOGIST. [Nov. 1, 1864. 



180 ON THE REVERSION AND 



I may, however, be asked, what proof I can adduce of disease and 

 change of colour ? As regards the existence of disease, there is no occa- 

 sion to reply, as the fact is only too well-known ; but as regards the loss 

 of colour, I have abundant evidence now before me. 



All those, indeed, who have had the least experience in the rearing of 

 fie silkworm must have perceived the occasional occurrence among the 

 brood of one or more dark grey or blackish brindled worms, contrasting 

 strongly and curiously with the pale sickly hue of the majority. These, by 

 the French cultivators, are called " vers tigres" or " zebres]' 1 that is, " tiger 

 or zebra-striped," and are regarded as a mere variety. Yet these are, in 

 fact, the original and natural worms. 



My attention having long since been arrested by this circumstance, 

 it at length occurred to me to endeavour by a series of experiments to 

 ascertain the cause, my conviction being, either that the species had at 

 some time or other been crossed by another of different colours, and 

 that Nature, as sooner or later she always will do, was making an effort 

 to separate them ; or that the original colour of the worm had in reality 

 been dark, and an effort was being made to revert from a sickly condi- 

 tion to the original healthy starting-point. Acting on this idea, I at 

 once determined to assist Nature by giving her fair play, and, conse- 

 quently, picked out all the dark-coloured worms and reared them 

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

 course was pursued with the white worms. 



Iu the following spring the one batch of eggs produced nearly all 

 dark brindled worms, while the other produced white ones, sparingly 

 interspersed as before with an occasional dark one ; these latter were 

 removed into the dark batch, which was at the same time 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 likewise 

 larger and better stuffed cocoons. 



Unfortunately, just as the eggs of the third year had been deposited 

 and collected, a violent and unexpected gale of wind suddenly upset the 

 whole, and irretrievably scattered them abroad. I had, however, seen 

 such good reason for hoping that I might eventually by this method 

 succeed in restoring the constitution of the worm, that I commenced de 

 novo, and went over the same ground again. 



The eggs with which my experiment was recommenced were pro- 

 cured in the spring of 1862 from Mr. Cope, of Umritsir, in the Punjab, 

 who assured me that they had just arrived direct from Cashmere, 

 although, from their appearance, I strongly suspect they owed " their 

 birth, parentage and education," to the Punjab, and had been sent by 

 mistake. But however this may be, on their arrival at Mussooree, I 

 submitted them to the microscope, which at once proclaimed them to be 

 ill-formed, discoloured, and diseased. 



This Mr. Cope denied ; nevertheless it was a fact, and as the worms 



