REPORT ON THE DISEASES OF SILKWORMS IN INDIA 



17 



the polar filaments are not shot out. Some workers claim to have 

 secured emergence of the filament by treating spores in this way 

 with digestive juice, but I have not found it possible under ordinary 

 experimental conditions. 



Suppose now that a silkworm has by some chance eaten leaf 

 contaminated with spores and these spores have reached the gut 

 of the worm and shot out their polar filaments. The next thing to 

 happen is for the contents of the spores to creep out of the spore 

 cases. We have already noted the spore contents in the stained 

 specimen as forming a ring round the inside of the spore case and 

 containing two nuclei. When this little mass of living matter 

 makes its way out of the spore, through the hole through which the 

 polar filament shot, it is seen as an exceedingly minute, somewhat 

 irregularly shaped body about 2/x in diameter if it were measured 

 in a somewhat rounded up condition (Text-fig. A, 3-6 ; and Plate 

 III, figs. 5 and 6). Of course such a tiny organism as this cannot be 

 studied except under high powers of the microscope and after having 

 been specially stained so that one can distinguish it from its 

 surroundings. But even with the greatest care it is only with 

 difficulty that the behaviour and structure of this body can be 

 observed, and therefore our knowledge of it is not nearly so complete 



Text-figure B. Diagram of cross-section of caterpillar. ' 



A, Ectoderm or outer skin. B, Hypodermis or under skin. C, Hsemocoele — the space, 

 filled with blood, in which the various organs lie. D, Eat body. E, Muscle. F, Dorsal 

 vessel or heart. G, Silk-gland. H, Excretory tube. I, Ventral nerve cord. J, Basal 

 membrane of gut. K, Epithelial cell of gut. L, Fibrillar fringe of gut cella. M, Peritrophic 

 membrane. N, Lumen of gut with leaf particles. 



