And what can be more easily understood than the presence of corpusculous parasites in the egg? The egg comes into existence during that marvellous phase of the life of a silkworm when, after having spun its cocoon, it sleeps within it as a chrysalis, resolving itself, so to speak, into those kinds of albumen and yelk from which the fully-formed moth will emerge, as a chick emerges from its egg. Let anyone imagine this origin of an approaching life, no longer in its normal purity, but associated with a parasite which will find in the materials surrounding it, so adapted to life and transformation, the elements of its own nourishment and multiplication. This parasite will be present when the eggs of the female moth, tender and soft as albumen, begin to define their outlines. Woe betide those eggs if they then enclose any particles of corpuscle, or of its original matrix. In vain will the envelope of those eggs become by degrees hard and horny; the enemy is within, and later on he will be discovered in the embryo of the silkworm. Thus this terrible plague is at the same time contagious and hereditary, helping us to understand the evolution of this double character in certain maladies both of men and animals. II. The first time Pasteur went to Alais the silkworm epidemic was universally attributed to a single cause--_pébrine_. _Pébrine_ was called _the disease_. This word expressed everything. It indicated the existence of a mysterious scourge, the origin and nature of which could not be traced, but which was ready to fall upon all the establishments devoted to the nurture of the worms. Whatever might happen, or whatever might be the cause of ruin in a silkworm nursery, _the disease_ was held responsible. One of the most striking proofs that the evil was attributed to _pébrine_ alone is found in the fact that a prize of 5,000 florins was offered by the Austrian Government in 1868, as a reward for the discovery of the best remedy for the prevention and cure of _pébrine_--'the epidemic disease which devastates the silkworm.'