No. 446.] PHO TIN US MA RGINEL L I S. 



uoLis with those of the dorsal layer. In ni;itc 

 dark granules of the dorsal layer cells ha\ c i 

 out, they are found equally in the cells sunouiK 

 of muscle. (Fig. i.) 



The ventral layer is composed of two distinct 

 called parenchyma cells, and the c\ lindcrs. Tl 

 enchyma differ from those of the dorsal layi 

 irregular in shape and size. Occasional cells 

 dorsal surface of the layer to the body wall. 

 In some cases the depth is several times the 

 thickness, while some cells are almost spheri- 

 cal. In some places the ventral layer is found 

 to be several cells deep. (Fig. 4.) The size 

 of the cells varies considerably. The graiui 

 lar secretion in these cells is much finer than 

 that in the dorsal layer. Max Schultze In- 

 stated that these granules are of non-uiau 

 composition. He examined the granules oi 

 both layers with polarized light, finding thai in. ,. 

 those from the dorsal layer were bi-refracti\ c. 

 but that those from the ventral layer were 

 not. Those of the dorsal layer having been ])ro\cd 

 to be of urate composition, he concluded the gra 

 ventral layer were non-urate. W ielowiejski verifiec 

 of these experiments, but did not agree with Ma 

 conclusions. He states that these e.\i)erinients n 

 the granules of the ventral layer to be in general 

 He thought, however, that the difference in conip- 

 be readily demonstrated by reagents. 1 ie found tin 

 the dorsal layer to be soluble in water but msoh 

 hoi, while the opposite was true of those of the v 

 Kmery says that the granules of the ventral layer ar< 

 line, and that they disappear altogether in balsam ' 

 The cells of the ventral layer appear to have moi 

 granular content in all of my preparations, inckuhni 

 material fixed in alcohol. It is only in osmic acid 1 

 cells are found comparatively free from such secrei 

 my sections are mounted in balsam, this medium wo 



