76 ZOOLOGY. 
body-walls), not always present, and end of the tentacles, 
and thus come in contact with animals forming their food. 
The ovaries and spermaries can be distinguished by their 
forming masses of closely convoluted tubes much thicker 
than the mesenterial filaments, and situated on the outside 
next to the free edge of each mesentery ; they are also of a 
pale lilac tint in Metridiwm marginatum (Fig. 50, 0). They 
are not easily distinguishable from each other by the naked 
eye. The figure shows at the base of the body the free 
edges of the mesenteries (m) of different heights, with the 
spaces between them through which the chyme passes into 
the body-cavity. For the com- 
plete passage of the circulating 
fluid the six primary mesenteries 
are perforated by a large orifice 
(op) more or less oval or kidney- 
shaped in outline (Fig. 50). The 
digestive sac is divided into two 
divisions, the mouth and stomach 
proper, the latter when the ani- 
mal is contracted being much 
shortened, and with the walls 
vertically folded, as seen in the 
ig. 50. — Partly aerate cut. 
sketch o: e anatomy of an Actinia 
(Atrium) with the, tentacles dis- In the tentacles are lodged the 
roportionately enlarged. 98, stom- < 
iy Ge, Wenieriek OF BAT lasso-cells or nematocysts, and 
fine a ts eceyese ” Sides through the tentacles are hollow, com- 
the septa.—-Drawn by J-S. Kingsley, municating directly with a cham- 
ber or space between the mesen- 
teries, and are open at the end. When a passing shrimp, 
small fish, or worm comes in contact with these tentacles, 
the lasso-cells are thrown out, the victim is paralyzed, other 
tentacles assist in dragging it into the distensible mouth, 
where it is partly digested, and the process is completed in 
the second or lower division of the digestive canal. The 
bones, shells, or hard tegument of the animals which may 
be swallowed by the Actinia are rejected from the mouth 
after the soft parts are digested. Pigment-cells, which are 
