THE TECHNOLOGIST. [Nov. 1, 1864. 



186 ON THE REVERSION AND 



temperature is high, the black worm is unknown, simply because the 

 heat of the climate, combined, perhaps, with too high a temperature in 

 the houses, enervates the worm and causes it to depart further from its 

 original type than it does in France, where the climate is colder and 

 more favourable to the general health of the insect. 



Again, the same writer informs us, that " in Lombardy the worm 

 which produces the white silk will constantly furnish nine white cocoons 

 to one yellow one, although in France, no matter how much care may 

 have been bestowed upon the worm, the yellow cocoons will always far 

 outnumber the white ones." 



Now, I have long entertained the idea that the production of white 

 cocoons is (except in cases where that colour is permanent in all cli- 

 mates) a strong sign of degeneracy, proceeding from weakness of con- 

 stitution, the rather that such white cocoons are always more abundant 

 where the temperature is high than in more temperate climates. Hence 

 in Italy the worms, which in that high temperature will constantly 

 produce an excess of white, will in a more favourable situation and 

 circumstances, produce an excess of yellow cocoons. Thus, the Boro- 

 pooloo of Bengal (B. textor, nob.), which there and in China, as a rule, 

 produces white cocoons, when reared in the colder climate of Mussooree, 

 yields almost all yellow cocoons ; while to find a white cocoon among 

 the worms of Cashmere (B. mori) is altogether the exception. 



Hence I come to the conclusion, that the whiteness of the worm and 

 the white cocoons are both indications of failing constitution, evi- 

 dencing the existence of a higher temperature and of a more thoroughly 

 artificial treatment than are conducive to the health of the insect. 

 Were the white or the yellow colour to remain permanent in all 

 climates and temperatures, the fact might reasonably be regarded as a 

 specific character, but where, as in the above observations, we perceive 

 these colours to be dependent upon temperature, we are compelled to 

 regard the change as entirely dependent upon the state of health. 



Thus heat, by causing debility, undermines the "constitution, and 

 gradually changes the natural colours, of both the insect and the silk 

 secreted by it, into a sickly white, while a restoration to a cooler climate 

 will, under proper management, restore the colours to their natural 

 shade, by imparting vigour to the drooping insect. 



Those wdio possess any real knowledge of the subject under discus- 

 sion will, I am fully aware, require no further proof of the worm's 

 deterioration than has already been furnished above ; yet as there are 

 not wanted some pretended savans, whose private interests prompt them 

 to conceal as much as possible maladies under which all our worms are 

 labouring, I shall proceed yet further .to show, even from their own 

 arguments, how very little they really know upon the subject. 



Common sense will at once point out that a worm imported from the 

 northern provinces of China will not long maintain its vigour in any 

 part of the hot lowland provinces of India, and indeed this is fully 



