FUNCTION OF THE (ENOCYTES OF INSECTS. 215 



various investigators were different species and very often 

 insects belonging to distantly related orders. Of course, the form 

 and body orientation of the cenocytes is quite different in non- 

 related forms and even in members of the same species at different 

 periods of their life history. This is exactly what we should 

 expect to find. In numerous cases, however, the varied opinions 

 can be attributed to the fact that many of the investigators did 

 not study the same cells. 



I have made sections of larvae of Trichoptera, Lepidoptera 

 and Diptera and find that the differences between their cenocytes 

 are merely differences of size, shape, density of granulation and 

 amount of ramification of the nuclei. Generally speaking the 

 oenocytes are large, yellow, more or less isolated cells, so large 

 in fact that in some forms they can be readily identified with a 

 pocket lens. They are located in the abdominal segments and 

 in such only as bear spiracles. Here the cenocytes are situated 

 behind the tracheae. They do not seem to be definitely attached 

 to the tracheae and sections do not reveal the intrusion of tracheal 

 filaments into these cells. A cytological study with the orange 

 G and iron hsematoxylin method shows the cytoplasm to be 

 finely granular and the nucleus to be greatly enlarged and rami- 

 fied, giving the cells the appearance of being highly active. 



To throw any light on the physiology of these cells was a 

 difficult task. Comparatively speaking, they are large, yet in 

 nearly all forms too small to deal with experimentally. To be 

 certain of any test one has to have a bulk of material and further 

 after obtaining it, one must be able to dissect out the organs 

 with ease and be certain at all times that they are the same. 

 Fortunately Mr. James W. Chapman, entomologist of the city 

 of Boston, called my attention to the larvae of the leopard moth 

 (Zeuzera pyrina). The life history of this caterpillar, as worked 

 out by Mr. Chapman, extends over a period of three years, during 

 which time it feeds on practically every species of tree or shrub 

 except conifers, and attains at the end of the third year a very 

 large size, accumulating a great amount of fatty tissue and con- 

 sequently becoming very heavy. On dissecting some of these 

 larvae, I found the cenocytes to be so enormous that in a three- 

 year-old larva, a cluster could be recognized with the naked 



