THE DISEASE OF THE MORTS-FLATS [fLACHERIe] 177 



cultures, which he had used for the production of eggs 

 because the worms did not contain corpuscles, ))ut which 

 showed, on climbing up the heather for their transforma- 

 tion, that peculiar sluggishness which he had sometimes 

 observed. As in the corpuscular disease, the malady 

 had not killed the progenitors, but was not the less 

 menacing to their descendants. 



Forgetting his discouragement, he set to work im- 

 mediately upon this idea. There were still in the 

 neighborhood some silkworm cultures attacked by the 

 disease of the morts-flats. He took the cocoons they 

 had yielded, satisfied himself of the absence of corpus- 

 cles, and obtained eggs from them. These eggs were 

 used for the preliminary cultures of the following year, 

 and as early as the 20th of March, 1868, he was able to 

 announce to Dumas that, out of the seven lots thus 

 selected from seven distinct cultures, six had miscarried 

 at various ages, especially in the fourth molt, with the 

 disease of the morts-flats. 



''Consequently, there is no more doubt," he added, ^ 

 "that the disease of the morts-flats can be hereditary 

 and attack a brood, independently of all conditions as to 

 mode of hatching of the eggs, ventilation of the brood, 

 excessive heat or cold to which the worms are exposed, 

 conditions which without doubt may occasionally pro- 

 voke this same disease. Hence, the imperious necessity 

 of never using for the egg-laying, whatever may be the 

 external appearance or the results of the microscopic 

 examination of the moths, broods which have shown 

 from the fourth molt to the cocoon, any languishing 

 worms, or which have experienced a noticeable mortality 

 at this period of the culture, due to the disease of the 

 morts-flats. I insist again on this advice, and with 

 more force than last year." 



^ Etudes sur la maladie des vers a soie, t. II, p. 232. 



