22 REPORT ON THE DISEASES OF SILKWORMS IN INDIA 



the developing embryo, when it is being broken down or digested, 

 a source of food supply is made available for the parasite and a 

 stimulus is provided in the digestive enzyme which causes the spores 

 already formed to dehisce. At all events dehiscing spores and 

 developing planonts and meronts are to be found in infected eggs 

 at this stage of development (Plate III, fig. 2). At the later stages 

 of development in the eggs when the yolk is nearly all used up and 

 when the embryo is nearly fully formed, meronts are no longer 

 numerous, but spores have been formed in various parts of the 

 embryo, especially in the gut, the hypodermis and what remains of 

 the yolk (Plate VII, fig. 3). Infection may be so heavy that the 

 hatching of the egg is delayed or totally prevented, but this would 

 be only in extreme cases. As a rule a young caterpillar already 

 pebrinised emerges from the egg. The infection is nearly always, at 

 least partly, a gut one, so that the young caterpillar is capable of 

 passing spores in faeces and so infecting other caterpillars, or of 

 still further infecting itself by auto-infection (Plate VII, fig. 4). 



There is another source of auto-infection which may. possibly 

 exist. Spores produced in various tissues or organs lying in the 

 heemocoele may possibly be set free into this space by the rupture 

 of the cell in which they were formed. It is not altogether 

 improbable that some of these spores may be acted upon by the 

 blood which contains a digestive ferment, and so planonts may be 

 set free in the hsemoccele. Pasteur believed that infection could be 

 acquired through wounds — the contaminated claws on the feet of 

 some caterpillars penetrating the skin of others over which they 

 crawled and carrying pebrine spores into the " body cavity," where 

 they dehisced. I must confess that this mode of infection appears 

 somewhat unlikely, and |xperiments tried by me to test this theory 

 have not succeeded, but it must also be noted that in some of my 

 preparations of highly diseased caterpillars from diseased moths' 

 eggs, spores and empty spore-cases and planonts have been found 

 in the hsemocoele. The importance of this can hardly be ignored : 

 it is an indication that spores probably do dehisce in the heemoccele 

 and this source of auto-infection cannot be neglected. As a source 

 of original infection toa in the way Pasteur indicated, it cannot be 

 quite ruled out of courtalthough it would in any case be a rare one. 



It is thus seen that in the vast majority of cases — if not in all — 

 the original infection is acquired by eating food contaminated with 

 pebrine spores. Infection is spread within the body of a caterpillar 

 once it is infected by auto-infection. Infection is spread from one 

 caterpillar to another by the spores passed to the outside in the 

 faeces or liberated from a diseased caterpillar or moth on its death 

 and disintegration. We have therefore now turn to the practical 



