386 University of California Publications in Zoology. t v L - 6 



to five times its ordinary depth. These nuclei, the "Matrix- 

 zellen" of Lonnberg, are richly supplied with chromatin. 

 Definite cell-boundaries can sometimes be seen; the cytoplasm 

 stains deeply and shows a granular structure. The writer Avas 

 unable to establish any processes running from these cells out 

 to the cuticula through the cuticular muscle-fibres, or to make 

 out any structural connection existing between cuticula and 

 subcuticula. The space between the subcuticular layer and the 

 longitudinal cuticular muscles is filled with very delicate muscle- 

 fibres (sag. fib.) and thread-like processes of the subcuticular cells, 

 taking in general a direction perpendicular to the surface. There 

 are also many fibres running parallel to the surface, as shown in 

 transverse section by their cut ends, but these are not so conspicu- 

 ous as the perpendicular threads. It was probably this layer 

 which Lonnberg mistook for the principal layer of the cuticula 

 in his sections. The writer has found similar appearances, due 

 to the fact that the cuticula is very easily affected by reagents. 

 In a specimen preserved in early stages of decomposition or 

 imperfectly fixed by the killing fluid, the cuticula is almost 

 invariably found to be sloughing off in thin strips, broken, 

 notched and ragged. It presents both horizontal and perpendi- 

 cular planes of cleavage, but shows a marked tendency to split 

 in layers parallel to the body-surface. This is the only indica- 

 tion of lamination noticed; it is more justly interpreted as a 

 splitting in the direction taken by the greater portion of the 

 fibres of which it is composed. 



The cuticula in the region of the rosette shows marked 

 changes. That lining the funnel is noticeably thinner, the 

 cuticular muscular layers are much reduced, and the subcuticular 

 cells are very few. As the much-folded margin of the funnel is 

 approached, the subcuticular cells of the outer wall also become 

 much reduced, sink deeper and cease to be a distinct layer; lying 

 within them large gland cells can be seen. In the writer's 

 opinion these are not related to the subcuticular cells but belong 

 to the central part of the body just as do the shell-glands and 

 the prostate glands, arising in the neighborhood of the inner 

 longitudinal muscular layer. 



The most prominent feature of the body-covering is the 



