304 NEW YORK STATE MUSEUM 



ural cavity without any adjacent liypodiTinal colls. Such a 

 cavit}' is represented on plate 28, liguie llccp in cross sectioui 

 and at figure Seep in longitudinal section. In the latter case it 

 will be noted that the cavity is continuous witli the ventral 

 cavit}' of the dorsal spines described above. In the drawings 

 representing the epithelium surrounding the cuticular pocket, 

 the outlines of the cells are not shown, because they could not 

 be made out with certainty on the preparations. Because of 

 the necessity for determining the homology of the threads of 

 protoplasm extending between the lamellae of the cuticular 

 pocket, whether more than a single thread arose from a single 

 cell, which could not be done, it was thought best to leave out 

 the cell boundaries. The preparations represented b}' the 

 drawings give one the impression that we have to do with 

 a syncytial structure, but it is not improbable that more care- 

 fully fixed material would show cell outlines. As it is almost 

 axiomatic that, wherever cuticular structures are found in the 

 Ilexapoda there are epithelial cells closely associated with the 

 cuticle from which they are derived, an explanation of the con- 

 ditions existing here is thought necessary. The hypodermal 

 cells, where they are adjacent to the cuticle and where they 

 inclose the cavity, are long and well marked, while the cavity 

 is filled with a homogenous, lymph-like staining structure. The 

 specimens studied were not originally Intended for histological 

 study; the entire larvae were dro])ped into hot water and thence 

 into either hot Perenyi's solution or hot vom Rath's picro- 

 sublimate. The first impression on studying this structure 

 was that it was an artifact due to improper fixation. But, 

 when several series had been examined and it was found that 

 the location and extent of the cavity was practically the same 

 in all, this explanation had to be given up as improbable. The 

 distance of the cuticle from the hypodermal cells sets aside 

 the possibility of its always having been a cavity and that the 

 structureless substance Avithin the cavity is blood, because, if 

 acce])ted, we have to meet the more difficult problem of ex- 

 plaining how the cuticle adjacent to Ihe cavity could have been 



