a carnivorous Tipulid larva. 248 
in the stomach; they are separated by spaces about 
equal to their own diameter. The annular muscles are 
internal and close-set. 
The epithelium of the stomach exhibits a very different 
appearance, according to the degree of secretory activity. 
I have compared my preparations with the descriptions 
and figures of Balbiani* and Gehuchten,t which are im- 
portant aids to the interpretation of the digestive ep1- 
thelium of Arthropods. A prolonged experimental 
inquiry is still required for the complete elucidation of 
the subject, and this can only be carried on by a student 
well practised in delicate methods of physiological re- 
search. Meanwhile, I offer such notes as I have made 
on the digestive epithelium of the Dicranota larva. 
The epithelium of the stomach is essentially a single 
layer of cells thrown into folds, which are very numerous 
and well marked in the anterior two-thirds, but subside 
towards the intestine. Indistinctness of the component 
cells often renders it hard to make out the folds. The 
cells are much narrowed at one or both ends, and closely 
applied to one another for the greater part of their 
leneth. The nucleus lies in the widest part of the cell, 
at any level from the base of the epithelium. A fascicu- 
late arrangement of the cells, such as Balbiani describes 
in Cryptops,t is not uncommon (fig. 16). 
The epithelium varies greatly as to its extension into 
the lumen of the tube. In some cases irregular exten- 
sions of the cells almost fill the cavity, especially at the 
cardiac end. When this happens, the boundaries of the 
cells become indistinct, or altogether invisible, and the 
protoplasm contains many rounded and highly refractive 
vesicles and granules (fig. 20). Transparent, granular 
prominences, such as those figured by Gehuchten§ in the 
“hase of active secretion,” are sometimes abundant 
(figs. 15, 19). 
Under some conditions there may be seen at the base 
of the epithelium of the stomach numerous large, nearly 
spherical cells (fig. 16), which resemble the mucous or 
* Etudes anatomiques et histologiques sur le tube digestif des 
Cryptops. Arch. de Zool. exp. et gén., Ze ser., tom. vill. (1890). 
} Rech. histol. sur l'appareil digestif de la larve de la Ptychoptera 
contaminata, le partie. La Cellule, tom. vi. (1890). 
t Loe. cit., fig. 26. 
§ Loe. cit., figs. 67 to 92, 
