Page:The history of silk, cotton, linen, wool, and other fibrous substances 2.djvu/149

 weigh many hundred thousand eggs, as well as follow out to the ultimate result his inquiries respecting their produce. He found that on an average sixty-eight sound silk-worm's eggs weighed one grain. One ounce, therefore, comprised, 39,168 eggs. But one twelfth part of this weight evaporates previous to hatching, and the shells are equal to one fifth more. If, therefore, from one ounce, composed of 576 grains, 48 grains be deducted for evaporation, and 115 for the shells, 413 grains will remain equal to the weight of 39,168 young worms; and, at this rate, 54,526 of the insects when newly hatched, are required to make up the ounce. After the first casting of the skin, 3840 worms are found to have this weight, so that the bulk and weight of the insects have in a few days been multiplied more than fourteen times. After the second change 610 worms weigh an ounce, their weight being increased in the intermediate time six fold. In the week passed between the second and third ages, the number of insects required to make up the same weight, decreases from 610 to 144, their weight being therefore more than quadrupled. During the fourth age, a similar rate of increase is maintained: thirty-five worms now weigh an ounce. The fifth age of the caterpillar comprises nearly a third part of its brief existence, and has been described, by an enthusiastic writer on the subject, as the happiest period of its life, during which it rapidly increases in size, preparing and secreting the material it is about to spin. When the silk-worms are fully grown, and have arrived at their period of finally rejecting food, six of them make up the weight of an ounce. They have, therefore, since their last change, again added to their weight six fold.

It is thus seen that, in a few short weeks, the insect has multiplied its weight more than nine thousand fold! From this period, and during the whole of its two succeeding states of being, the worm imbibes no nourishment, and gradually diminishes in weight; being supported by its own substance, and