May IS. 191S Wilt of Gipsy-Moth Caterpillars 1 1 1 



Although these bodies are not formed within the nuclei of muscle, 

 nerve, excretory, and glandular cells, it is not the intention to imply 

 that no changes at all take place within these, for such is not the case. 

 Their chromatin shows signs of degeneration, such as the flowing together 

 into lumps, but the little reddish-staining granules were never found 

 within them. This leads the writer to believe that the little granules 

 are not products of nuclear disintegration — if they were, one would 

 expect to find them within these nuclei also — but that they are of etiologi- 

 cal significance. While, of course,- they may be the vegetative stages and 

 the polyhedra the resting stages of an unknown organism, there is 

 nothing tangible which would substantiate the view that the polyhedra 

 are directly related to these granules. The latter are not identical with 

 those appearances described as being within the polyhedra (p. 106). It 

 will be shown later in this paper that the virus passes through the pores 

 of the Berkefeld filter, and since such a filter holds back polyhedra one 

 might say that these have been satisfactorily eliminated and therefore 

 are of no etiological significance ; but this, it seems to the writer, is a nar- 

 row view to take of the subject. The Berkefeld filtrate revealed little 

 dancing granules which may be identical with those observed within the 

 tissue nuclei. Now, as before stated, these filterable granules may be 

 the vegetative stages and the polyhedral bodies the resting stages of an 

 organism ; or the polyhedra may be a secretion of a minute organism con- 

 tained within. As long as there is no evidence, however, that the poly- 

 hedral bodies are directly related to the filterable virus or to the little 

 granules, the view that they are reaction products appeals more strongly. 

 The virus invades the nuclei of the hypodermal, fat, tracheal matrix, and 

 blood cells, and the polyhedral bodies arise, perhaps, as by-products of 

 nuclear digestion and disintegration. When these four tissues disintegrate, 

 it is an easy matter to conceive the disorganization of the remaining tissues, 

 and, as stated pre\dously, the intestine seems to be one of the last organs 

 in the body to be so affected. 



The questionable little granules should not be confused with the pig- 

 ment granules occurring in the hypodermal cells and in the ganglia. 

 Since the pigment granules are larger and are never found within the 

 nuclei, unless carried there by the microtome knife, they are very easily 

 distinguished. Furthermore, the ordinary protein bodies often occurring 

 in the spaces of the fat body and easily demonstrated by haematoxylin 

 must not be taken for polyhedral bodies. Protein bodies stain perfectly 

 black with hematoxylin, are of a round or a regular shape, and are never 

 found within the nuclei. 



Polyhedra have never been found in the intestinal lumen. One would 

 often expect to find them there, especially after artificially feeding 

 polyhedral material to caterpillars, but this does not prove to be the 

 case. However, their absence may be explained by the obser\^ations of 



