1902.] NATURAL SCIENCES OF PHILADELPHIA. 309 



formed precipitating in the form of granules which, as we have 

 said, ma.sk the true sti'ucture of the cytoplasm. On this hypothesis 

 an explanation Is readily affoi'ded for the varying strength of the 

 palisade in different individuals. When very strong — i. e., com- 

 posed of thick fibres from the intervals between which the c}'to- 

 plasm has withdrawn — the very evident "striated border" 

 described by so many authors is present. In such cases we may 

 suppose the animal to be approaching a moult. When the palisade 

 is scarcely, %'isible (fig. 11, ^) a moult has probably occurred 

 shortly before feeding. 



In the case of moulting figured (fig. 8) the intestine was taken 



Fig. 8. —Median cell X 600 from intestine of Oniscus asellus, fixed in 

 sublimate acetic immediately after moulting the chitinous intima. The 

 lower part of the cell is filled with chitinogenous substance in granular 

 form. All fibres have disappeared from this side of the cell. Intima is 

 very thin. 



forty-two hours after feeding. The quantity of food in granular 



form on the luminal side of the intestinal cell at this time is usually 



small, and when it does occur the granules can be distinguished 



from those of the chitinogenoiL*! substance. The latter are smaller, 



nearly uniform in .size, equally distributed and very abundant. 



AVhile I have not been able to trace all the steps in this process, it 



seems probable that there is here a dissolution of fibres in some 



points like that described by Mathews (23) for the zymogen of the 



pancreas of many vertebrates.* The new intima is laid down by 



some process of hardening of the chitinogenous substance. 



* To any one familiar with Mathews' paper the dift'erence will be 

 obvious. The zymogen granules he derives directly from the fibres, 

 which are traceable in some cases to the chromatin. Granules may 

 occur here previous to precipitation by the killing fluids. 



