146 Silkworms in India. [Vol L 



"2. Muscardine, which is never hereditary, unless the motbs mingle with 

 worms covered with the spores of the Potrytis, in which case the 

 moth might also catcli the disease, and its general debility decrease the 

 vigour of its progeny. 

 "3. Flaccidity, which is hereditary in an indirect manner, a debility springing 

 from the affection of the parent rendering its issuejmore apt to succumb 

 to disease. 

 " 4. Pebrine, which is hereditary in the true sense, the corpuscles passing from 

 the mother through the egg to the next generation. 

 " In the production of eggs, then, we need look for flaccidity and pebrine only, the 

 other diseases not entering into the consideration. 



" Reproduction.' — The simple process formerly employed in all sericultural countries 

 consisted in stringing tbe cocoons and letting the moths couple, as in the modern 

 process. A sheet was then hung up with the lower edge so turned as to form a trough 

 into which any badly gummed eggs might fall. After uncoupling, the females were 

 placed upon the sheet and permitted to lay their eggs promiscuously. The only precau- 

 tion taken against the disease was in the selection for reproduction of lots of cocoons 

 whose larvae had shown no signs of any malady, and which were themselves of first 

 quality. From what has been said it will at once be seen that pebrine contracted 

 after the fourth molt, and the slow form of flaccidity due to the presence of chain 

 ferment, are not thus guarded against. The modern system has a deeper, more 

 scientific basis, and aims to guard against these. 



" The Pasteur system of microscopical selection.'— As we have seen, pebrine and 

 flaccidity are the only two diseases which it is necessary to guard against in selecting 

 eggs. If pebrine or flaccidity have appeared in a positive form in the larva;, either 

 through the external or internal symptoms described in the last chapter, no further 

 examination need be resorted to, as the stock will evidently be unfit for reproduction. 

 The most important and positive sign of the latter disease to be looked for is languor 

 at the spinning time. If a greater degree of certainty is desired, or if the egg-pro- 

 ducer has not had the opportunity of observing the rearing of the worms, mi- 

 croscopical examination of the chrysalis may be resorted to. In flaccidity this 

 examination should be confined to the stomach, where the chain ferment to be 

 sought for is more easily.found. M. Pasteur [Etudes, 6[c., Volume I, page 233) gives 

 the following directions for extracting this organ : ' Cut away the walls of the thorax 

 of the chrysalis with fine scissors after the manner shown in the figure 1 so as to 

 reveal the stomach. Draw this out with a pair of tweezers. The restricted part of the 

 digestive tube, which unites the stomach with the urinal sack, u, should then be cut. 

 The anterior part of tbe digestive tube now aloue holds the stomach in place, and this 

 easily gives way. Lay the small ball thus withdrawn on a glass slide and scratch 

 away the very soft, fatty envelope which covers the interior. Of this interior substance 

 take a piece as big as the head of a pin, wash it with a drop of distilled water, and 

 placing it upon a slide with a cover glass over it, examine it with a microscope magni- 

 fying about four hundred diameters. With a little experience this work may be done 

 very rapidly. It would be well to take out at the same time the stomachs of, say, 



twenty chrysalides, and lay them on as many glass slides The first few days after 



the formation of the chrysalis the contents of the stomach are generally very liquid, 

 which makes their extraction inconvenient. It is better to make these observations 

 seven or eight days after the spinning begins, when the matter will be found to have 



1 Plate IX figure 3. 



