NATURE OF POLYHEDRAL BODIES FOUND IN INSECTS. 373 



stain more readily than the underlying strata. From these 

 staining reactions it becomes apparent that the polyhedra are 

 complicated in structure, and do not therefore differ essentially 

 from what Bolle and Prowazek found to be true of the silkworm 

 polyhedra. Our observations on the staining reactions also show 

 that morphological studies do not enable us to regard the poly- 

 hedral bodies as organisms. We believe that the polyhedra, are 

 protein degeneration-products of the disease. The staining re- 

 actions have demonstrated that they are not simple crystals, 

 but complicated in structure, and have a tough outer layer. 

 Consequently, and for a number of other reasons, we do not 

 believe them to be true crystals and therefore choose to call 

 them pseudo-crystals. The variations in their staining reactions 

 which one obtains at times can well be accounted for by assuming 

 that one is dealing with different stages in the synthetic process 

 of pseudo-crystals. Another matter militating against the idea 

 that the polyhedra are organisms is the fact that Glaser ('15) 

 and Chapman and Glaser ('16) have experimentally demon- 

 strated the possibility of infecting healthy gipsy moth cater- 

 pillars with wilt material from which the polyhedral bodies were 

 removed by passing the virus through Berkefeld Grade "N" 

 candles. We have shown that wilt is caused by a filterable virus 

 and believe that the polyhedra arise as a reaction against the 

 invasion of this virus. 



ORIGIN OF THE POLYHEDRAL BODIES. 



Studies on sectioned gipsy moth, army worm and tent cater- 

 pillar material have shown that the polyhedra originate within 

 the nuclei of the hypodermal, fat, tracheal matrix, and blood 

 cells. (Fig. 2.) In the true army worm, however, polyhedra 

 are at times formed within the nuclei of intestinal epithelial 

 cells. We have been utterly unable to find the bodies within 

 the nuclei of muscle tissue, Malpighian tubes, ganglia, nerves, 

 cenocytes, salivary glands, gonads and within the intestinal 

 epithelial cells of all forms except the true army worm. 



The formation of the polyhedral bodies within the nuclei of 

 the four tissues above mentioned and the visible changes taking 

 place within these nuclei may be described as follows: The first 



