When the insect has finished its labor of unwinding, it smears the entire internal surface of the cocoon with a peculiar kind of gum, very similar in its nature to the matter which forms the silk itself; and this is no doubt designed as a shield against rain or the humidity of the atmosphere, for the chrysalis in its natural state; when of course it would be subject to all varieties of weather. The silken filament of which the ball is made up, is likewise accompanied, throughout its entire length, by a portion of gum, which serves to give firmness and consistency to its texture; and assists in rendering the dwelling of the chrysalis impervious to moisture. This office it performs so well, that when, for the purpose of reeling the silk with greater facility, the balls are thrown into basins of hot water, they swim on the top with all the buoyancy of bladders; nor, unless the ball be imperfectly formed, does the water penetrate within until the silk is nearly all unwound. In figure 4, plate III., the cocoons are drawn two-thirds of the usual size, and are shown with part of the outward floss silk removed. The continual emission of the silken material during the formation of its envelope, together with its natural evaporation, uncompensated by food, causes the worm gradually to contract in bulk; it becomes wrinkled, and the rings of its body approach nearer to each other and appear more decidedly marked. When the ball is finished, the insect rests awhile from its toil, and then throws off its caterpillar garb. If the cocoon be now opened, its inhabitant will appear in the form of a chrysalis or aurelia, in shape somewhat resembling a kidney-bean (See Figure 5. plate III.), but pointed at one end, having a smooth brown skin. Its former covering, so dissimilar to the one now assumed, will be found lying beside it. The account which has been given of the progressions of the silk-worm shows, that, in its various modifications, _the animal organization of the insect has been always tending towards its simplification_. Count Dandolo, writing upon this subject, observes, “Thus the caterpillar is in the first instance composed of animal, silky, and excremental particles; this forms the state of the _growing caterpillar_: in the next stage it is composed of animal and silky particles; it is then the _mature caterpillar_: and lastly, it is reduced to the animal particles alone; and is termed in this state the _chrysalis_. The poet Cowper, in the following lines, beautifully illustrates this subject: