76 BRITISH TYROGLYPH1D.E. 



portions of the cseca of the ventriculus itself, and has 

 thus been prepared for absorption ; the fluid portions 

 of the prepared food are absorbed into these elongated 

 cells by endosmosis. The cell becomes crowded with 

 droplets of fluid prepared food, the digestion and 

 elaboration of which takes place within the cell itself ; 

 the cell now swells at its distal (inner) end and becomes 

 clavate ; they either continue to project straight into 

 the lumen or the clavate portions bend over the un- 

 elongated cells next to them, if there be any. The 

 clavate portions also become filled with food droplets, 

 and the whole of the finally elaborated nourishment 

 passes by exosmosis through the outer walls of the 

 cells and the tunica propria into the general body 

 cavity, where it mixes with the blood. When the 

 nourishment has passed out of the clavate portion of 

 the cell a constriction arises at the proximal end of 

 the clavate portion, that portion becomes more or less 

 globular, the constriction increases ; until finally the 

 inner globular portion of the cell, which has become 

 large, breaks off and falls into the lumen of the ven- 

 triculus. These cells are empty, or nearly so, except 

 that a certain amount of excretory matter is left in the 

 cell ; this crystallises or forms small concretions, many 

 of which have existed before the food droplets have 

 entirely left the cell ; these are a portion of the white 

 opaque excretory matter so abundantly present in the 

 Acarina, and usually looked upon as being of a urinary 

 nature. The cells lie quite loosely in the ventriculus 

 and in the cseca, which are often full of them (PL C, 

 fig. 10), but they gradually crumple up, and in such 

 Acari as the Tyroglyphidae, Oribatidse, etc., where the 

 passage from the ventriculus to the anus is by a hind 

 gut fitted to pass solid dejecta, they form a part of 

 the balls of excremental matter found in the colon and 

 rectum. Nalepa says that in T. lonyior these balls can 

 be shown by micro-chemistry to contain uric acid 

 abundantly, but not in a concretionary or crystalline 

 condition. 



