THE SILKWORM 75 



the body and the chitinous cuticle, become telescoped inwards. 

 In the resting larva within the cocoon, all the characteristic 

 organs of the moth are pretty near completion. The muscles 

 and nerves, it is true, are still rudimentary, and the new parts 

 are soft and white, but they are taking their final shape, and 

 having now gained additional space owing to the emptying of 

 the silk-glands and the relaxation of the dead larval skin, they 

 project from the external surface much as they do in the moth. 

 An old experiment of Swammerdam is instructive on this 

 point. Take a resting silkworm, dip it for a few seconds into 

 boiling water, and then strip off the larval skin. The new 

 head, with its compound eyes and feelers, the wings, and the 

 long, slender, many-jointed legs will be found within, either 

 more or less sunk into the body, or completely protruded, 

 according to the age of the larva. At length, in the natural 

 course of events, the larval skin bursts, the moth, clad in a 

 temporary, transparent, and close-fitting pupal skin, emerges, 

 folds its long appendages slowly into a symmetrical position, 

 so that they may be supported without crowding or overlaying, 

 and then exudes a sticky fluid, which hardens rapidly and 

 binds all together. In a few hours the pupa is covered with a 

 firm brown varnish, which protects it from injury, and, at the 

 same time, renders it incapable of any but the most limited 

 movements. 



Internal growth still proceeds, the last details of the tissues 

 are elaborated, the surface of the imprisoned body acquires its 

 appropriate ornaments, and then one last moult sets the moth 

 free. It generally makes its escape early in the day, from a 

 fortnight to three weeks after spinning up. As soon as the 

 head finds itself impeded by the interwoven silk, a fluid 

 (probably secreted by the sali'Vary glands) is projected from the 

 mouth. This softens the fibres, which are then easily dis- 

 placed. The moths shun the light ; their mouths close, and 

 there is no more solicitude about food. Mating and egg- 

 laying are the sole business of the few days which remain 

 to be spent. 



In the ordinary course of business the breeder now pro- 

 ceeds to select the best cocoons for egg-production. The rest 

 are sorted; those containing dead worms, besides doubles 

 and other malformations, are put aside ; cocoons not required 

 for breeding are killed by heat, and the winding of the silk 



