Restoration of the Silkworm. 147 
terming cultivation, without one single renewal or infusion of the 
original healthy and natural stock from which the race has 
descended! ‘Truly has it, as Darwin would say, undergone “ the 
struggle for existence!” 
One would almost be tempted to think, that the object of cul- 
tivators had actually been the destruction of the insect, for in 
what other department would breeders so long have neglected to 
infuse new blood into their domestic stock? Is it not a well 
understood and long-established fact, that, whether among 
animals or plants, an occasional renewal of seed and re-infusion 
of the original stamina is found to be absolutely necessary for the 
preservation of health, and of that particular standard of per- 
fection which it is thought desirable to maintain? And yet with 
the domesticated Bombyx Mori, this necessary precaution has 
been uniformly neglected for 4,500 years! What wonder, then, 
that under the combined effects of bad and scanty food, want of 
sufficient light and ventilation, too high a temperature, and with 
the constant and unvarying interbreeding of a debilitated stock, 
the insect should have become subject to a multitude of maladies, 
and threaten, at no distant period, to become extinct! 
By here condemning the system of interbreeding, I must, how- 
ever, guard against the possibility of being misunderstood, for I 
am well aware that in France a very senseless outcry has been 
raised in some quarters against the interbreeding of brother and 
sister, and other near relatives, as if, in a state of natural freedom, 
such a proceeding was not the general and authorized rule. 
What I condemn, and in this I am happy to find myself sup- 
ported by such weighty authority as that of M. Guérin-Ménéville, 
is not the intercourse of near relations, but the incessant inter- 
breeding of diseased and debilitated individuals, which, as “like 
produces like,” cannot possibly do otherwise than perpetuate and 
aggravate both disease and debility. Where brothers, sisters 
and cousins are all healthy and of sound constitution, no bad 
consequences will ensue from their interbreeding, for such is the 
established plan upon which nature acts; but where disease 
exists, the breeding from two deteriorated individuals, whether 
they be nearly or distantly related, will only add fuel to the fire, 
and perpetuate, and even aggravate, disease. 
I assert, then, that there is no such thing now in existence as a 
perfectly healthy domesticated stock of silkworms, the colour 
proving, beyond all doubt, that the constitution has been utterly 
destroyed, and the wonder rather is, that the worms have con- 
tinued to live so long, and to yield such good returns under such 
VOL. Il. THIRD SERIES, PART Il.—AuGUST, 1864, M 
