WAX GLANDS OF THE COCKROACH 565 



examining the dorsal wall of the abdomen of males in different 

 stages of development. He found that the hypodennis was not 

 always made up of two layers of cells as Minchin described, but 

 sometimes showed a single layer of cells, other times two or more 

 layers. In the intersegmental areas, he found a single layer of 

 cells as Minchin described. Where the muscle bundles were 

 inserted he also found a single layer of cells, modified in the usual 

 way to form the characteristic muscle attachments. In other 

 places the hypodermis consisted of a single layer of cells, usually 

 of small size, or of two layers, the upper layer consisting of small 

 cells, the lower one of much larger cells, or of several layers of 

 cells arranged without order. Except for an occasional large 

 cell at the surface among the smaller cells where a single layer 

 of cells w^as present, the majority of the larger cells were below 

 the smaller ones. 



He concluded that these cells were not to be considered as 

 nerve cells, but as cells of an epithelial nature, derived from the 

 upper layer of the hypodermis, but which had undergone en- 

 largement and were no longer of use in the secretion of the cu- 

 ticula. He was uncertain whether these large cells were hair- 

 forming cells or gland cells, but because of the structure of the 

 nucleus and protoplasm he favored the glandular view, the in- 

 sects probably secreting an oily substance. He, therefore, con- 

 cluded that the hypodermis of the cockroach did not differ from 

 that of other insects by the nature of the cells which composed 

 it, but only because, as the insects increase in size, many hypo- 

 dermal cells become specialized for a particular function, in- 

 creased in size, took on a branching form, and were carried below 

 the regular hypodermis, thus forming an apparently double- 

 laj^ered hypodermis. 



In 1909, Berlese, in commenting on this peculiar structure in 

 the cockroach, stated that if the smaller cells were not merely 

 infiltrated amoebocytes, they were to be regarded as a prolifera- 

 tion of the hypodermis, and that possibly the larger cells had 

 assumed another function. At least, he was sure that the con- 

 dition was unique among insects and w^as still an open question. 



