Eolis has no liver. With so much stomach it can carry on the process of digestion-without the aid of that organ, so troublesome to man and beast. A row of hepatic cells extending part way along the intestine represents the rudiment of a liver, or its vestige.
Where are the lungs? Nowhere—or, rather, everywhere. No part is specialized and set apart for aërating the blood. In the vital economy of this sea-slug, there is but little division of labor. The surface is soft tissue, covered with vibrating cilia, and currents of water, set in motion by the cilia, How around the tissue and yield oxygen to its blood.
Perhaps the gelatinous knob you detached was not an Eolis, If your knife reaches a stomach which is not arborescent, you may have a Doris. The dorsal papillæ of Doris are genuine lungs, but they breathe for only part of the body. They aerate only the blood which goes to the liver, an organ which appears now, not as a row of bile-cells, but as a well-defined gland. The foot shares the labor of the lungs, they breathing for the liver, it for the rest of the body.
Fig 1.—Doris Lacina.
In Eolis the quill-like diverticula of the stomach are placed in rows; in Doris the leaf-like, moss-like, or flower-like branchiæ are gathered into clusters (Fig, 1). Our first woodcut represents a Doris (Doris lacina), with two horn-like antenna on the head; and on the back, at the other extremity, a tuft of crimson leaves finely reticulated and deeply lobed. The second cut represents a Doris (Doris plumulata), with frond-like antennæ and a lung resembling; tufts of delicate sea-weed wrought into an eight-rayed star. Another Doris wears its lung like a brilliant flower, another like a begemmed tiara, Doris can draw his lungs into his body or throw them out at pleasure (Fig. 2),
Dendronotus may be known, as its name implies, by its branching, tree-like gills. If we leave the rocks and wharf-posts, and examine the laminaria (oar-weed), or ulva (sea-lettuce), we may find another member of this family. Aplysia is known to fishermen under the name of "sea-hare." A hump on its back calls up the image of a camel rather than that of a hare. If you make a dissection you will find that an idea has been borrowed from the camel's stomach as well as
