Contagious Diseases of Insects. 263 



the infinite multitude of these which gives to the fluids of the 

 diseased caterpillar their milky look, and likewise, unquestiona- 

 bly it is they which cause the ashy appearance of the surface, the 

 skin being thin and delicate, so that the color of the fluid con- 

 tents shows through. The diseased blood is so thick with 

 these minute corpuscles that little else can be ordinarily seen in 

 it. Sometimes, however, degenerated lymphoid corpuscles of 

 the blood will be noticed, recognizable by their size and spherical 

 contour, but differing from the normal corpuscles in their darker 

 tint and coarsely and irregularly granular structure. These 

 darker, granular corpuscles are always dead, no longer exhibit- 

 ing amoeboid movement, and have usually a spherical form. Not 

 infrequently debris of the fatty bodies is apparent in the form 

 of large irregular cells, floating freely in the fluid, but these 

 cells themselves will be found to contain immense numbers of 

 the minute spheres already mentioned. In fact, if a little 

 portion of the soft remnant of the fatty bodies be removed, 

 spread upon a cover, and examined with a power of a thousand 

 diameters, it will be seen that the cells of these organs are the 

 seat of an extreme degeneration, the entire contents of many of 

 them being wholly replaced by the spherical granules mentioned 

 above. Occasionally a cell containing a nucleus will be found, 

 but more commonly all distinction of contents has disap- 

 peared.* 



* As an example of the condition of the fatty bodies, I will 

 describe those of a larva examined October 9, whitish in color and 

 nearly dead, making little effort to escape. A^droplet .of the blood 

 exuding from a small cut made in the back was alive with the 

 minute spherules already mentioned, and contained also noticeable 

 numbers of dead blood corpuscles in a dark, spherical, granular 

 condition, together with a few unaltered examples still capable of 

 amoeboid movement. 



A fragment of the fatty bodies examined, consisted chiefly of 

 pale spherical cells, 1.5^ to 7.5// in diameter, resembling oil globules, 

 except that they had not the high refractive index of fat. A few 

 of these globular cells were very pale and indistinct, the contents 

 very indefinitely granular and often with a large spherical nucleus 

 likewise very pale ; but most of them were more or less completely 

 filled with dancing spherules, slightly different in size in different 

 cells, these differences having, however, no relation to the proper 

 size of the cells. Sometimes there were not more than twenty-five 

 or thirty such granules in an optical section of a large cell, the con- 



