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The .cocoons spun on these branches of heather ought to be 
large, heavy, and well-shaped. The good cocoons are regular ; 
their ends are rounded and not pierced; and they are hard, 
























































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Fig. 214.—Spherical cocoon Fig. 215.—Cocoon of Bombyx mori, 
of the Bombyx mori. drawn in towards. the middle. 
especially at their extremities, and have a fine grain. ‘They are 
cylindrical. The best are drawn in towards the middle, or have 
a concavity on either side of it (Fig. 215). Every one knows 
that there are white and yellow cocoons. They are the produce 
of different races of worms. 
Commerce recognises two kinds of white silk: the first white 
and the second white. The silk of the first white is produced by 
the race Sima, the cocoons of which are of a perfect and azured 
white. They produce the most beautiful and most precious silk, 
and serve for the fabrication of light and delicate coloured tissues. 
The silk of the second white is furnished by two races: the 
Lspagnolet and the Roquemaure. 
The races that produce yellow cocoons are more numerous than 
the white ones. The yellow races are divided into three greups : 
those that have small, middle-sized, or large cocoons. The first 
and second are stronger, and more esteemed than the last. 
The greater number of the races of silkworms have, let us 
here mention, white and yellow cocoons; there are some, how- 
ever, whose cocoon is of a greenish white, or even quite green, or 
