Silkworm from Japan. 393 
country. We know but little of its habits, and the efforts to rear 
and acclimatize this valuable race are of necessity a number of 
experiments, of which some fortunately have been successful, but 
the majority were the reverse. It is only by narrating the minu- 
tie of treatment, by carefully noting the temperatures, the atmo- 
spheres to which the insects are exposed from the egg to the perfect 
state—by comparison of their food plants and the various modes 
of feeding them, that we shall be placed in the best condition 
eventually to attain success. There can be no doubt in the first 
instance that the treatment of the ova during the long period of 
winter, and especially in the spring months, is of the highest import- 
ance. It must be that the nearer we approach to the natural con- 
dition of the insect in its wild state, the greater our chance of 
success ; and the heated temperature and want of aération which 
the eggs must undergo during their two months’ voyage to Europe 
from Japan must materially impair their vitality. Next it is evi- 
dently of the greatest importance to be provided with young oak 
buds and leaves just bursting at a time when the larve hatch out. 
For this a double precaution is necessary ; Ist, to foree young oak 
trees in pots under glass, some to a greater and some to a less 
degree, so that foliage may be ready for the young worms; 2ndly, 
to keep the eggs ina well aérated cool place, at a temperature not 
if possible exceeding 50°, till the oak trees are breaking out of 
doors. As this is the natural period for the exit from the egg, it 
would seem to be the proper time to place the ova in a warmer 
but moist atmosphere for hatching out, imitating in fact the natural 
temperature out of doors. It is stated by French writers that the 
eggs should not be exposed to frost during winter, but I cannot 
concur in this statement until it is proved by actual experiment, 
since I am informed that the climate of Japan resembles that of 
this country, and that severe frosts occur there, and to these 
during the winter the egg would in a wild state be subjected. 
Again, covered as it is with a stout shell and a thick coating of 
gum, it by no means follows that frost would penetrate to the 
larva inside; while, lastly, larvae have been frozen again and again 
with impunity. In the treatment of the larve great stress is laid 
by French experimenters on maintaining them if possible on the 
living tree exposed to free aération ; they maintain that the skin of 
the larva is very porous, and that it is necessary to its well being to 
inhale a large supply of air; and further that when the oak sprays 
are placed in water, and too great a proportion of water is drawn 
up into the leaves, the alimentation of the insect is carried on in 
