150 PASTEUR: THE HISTORY OF A MIND 



itself with a resistant tunic, in the interior of which all 

 the tissues seem to fuse into a pulp of homogeneous ap- 

 pearance. It is in the midst of this magma that, little 

 by little, the tissues of the moth are formed and become 

 differentiated. 



The moth has only a rudimentary digestive canal, 

 for it no longer has any need of eating: the worm has 

 eaten for it. It has wings, but, in our domestic races, it 

 makes no use of them. It is destined only for the re- 

 production of the species, and the sex-union takes place 

 as soon as it comes out of the cocoon. The female then 

 lays a very considerable number of eggs, which may 

 reach 600 or 800 and in the races that we call annual, 

 which are the most sought after, this "graine" does 

 not hatch the same year as its production. It is de- 

 layed till the reawakening of vegetation the spring of 

 the following year. 



It is only when the grower wishes to have "graine" or 

 to induce the laying of eggs (faire grainer) that he awaits 

 this coming forth from the cocoon, in which the trans- 

 formation of the worm into a moth requires about 15 

 days. By adding thereto the 35 or 40 days required 

 for the culture of the worm, and the time necessary for 

 the laying of the eggs, we see that the complete evolution 

 of the silkworm, from the egg around to the egg is about 

 two months. The period of industrial life is sensibly 

 shorter. When the grower wishes to use only the cocoons, 

 he must not wait till the moth, in coming forth, has 

 opened them and thereby rendered them unfit for spin- 

 ning. They are smothered 5 or 6 days after they have 

 climbed the heather twigs. That is to say, the cocoons 

 are put into a vapor bath in which the chrysalids are 

 killed by the heat. For the silk grower, in this case, 

 scarcely six weeks separate the time of egg-hatching 

 from the time when he carries his cocoons to market 



