14 CULTURE OF SILKWORMS. 



selection of "firsts," they would yield, say, 240,000 ec^q;s* or 

 120,000 female " sccoutls," wliicli again would yield 24 millions 

 of eggs for distribution. This number of worms would give 

 l()-458 tons of " green " cocoons, or at four broods per annum, 

 say 64 tons, as the outcome of the work of a single microscoj)ist 

 for a year. This is as much as a hundred microseopists could 

 do, with multivoltine worms, if working by the ordinary method 

 of selection as practised in Europe. 



The whole system depends on guarding from external 

 sources of contagion the generation after that which has been 

 ]»roved to be free from disease by microscoincal examination. 

 To do this, cleanliness, the free use of antisei)tics, isolation, and 

 the growing of the food in a place where it will not be infected 

 by imhealthy worms, are the main points to be attended to. As 

 a j)recautionary measiire, the " firsts " might be divided advan- 

 tageously, and kept in two sei^arate houses. 



From time to time it might be necessary to introduce fresh 

 blood into the breed, and for this purpose the fresh worms 

 should be microscopically selected for four or five generations 

 before mixing them with the original " firsts," being kept 

 during their })robation in a house isolated from all the others. 

 It may be mentioned here that I have found that a single selec- 

 tion, never mind how carefully it is done, is insufficient to elim- 

 inate pebriue from a race of worms. Therefore it follows that 

 it is useless to attempt to produce " seconds " until the " firsts " 

 have been thoroughly purged of all traces of disease, by 

 repeated selections. 



In an establishment such as is here suggested, the micro- 

 scojdst would be the only highly paid man. All the other work 

 could be done, after a little time, by ordinary coohes, so that 

 the cost of maintenance would be comparatively unimportant, 

 and the eggs could be sup2>lied at a low price. 



I venture to think that this system, if carried out properly, 

 will do for the multivoltine silkworms of the tropics what the 

 system practised in Europe has done for the annual silkworms 

 of temperate climates. 



SELECTION BY LONGEVITY. 



Mr. E. Blechynden communicated to me a plan he has lieen 

 trying, to effect the selection of healthy worms for breeding 



* A female of hoiiihijx sinensis I liiid lays on an avera<j:(; 355 egtrs, 

 weiu'luniiC 2'414 j^ruins; ItiU moths would lay one ounee of eu;gs, the standard 

 ounce being 15 gi'ams or 385"S grains. In the above estimates it has been 

 assumed that each moth will prodiice only 2U0 worms. 



