. Elements of Comparative Anatomy. LIVER OF MOLLUSCA, 365 lu the Placopliora it forms a paii' of symmetrically disposed branched tubes. lu the Gastropoda this gland is no less Avell developed. In the shelled forms it occupies the largest portion of the visceral sac within the shell; it is always made up of a number of large lobes, and embraces more or less of the enteron. The bile-ducts from the lobes either open separately or together into the first portion of the mid-srut, and sometimes also into the stomach-like enlaro:ement. The numbei', as well as the relative size of the separate portion
. Elements of Comparative Anatomy. LIVER OF MOLLUSCA, 365 lu the Placopliora it forms a paii' of symmetrically disposed branched tubes. lu the Gastropoda this gland is no less Avell developed. In the shelled forms it occupies the largest portion of the visceral sac within the shell; it is always made up of a number of large lobes, and embraces more or less of the enteron. The bile-ducts from the lobes either open separately or together into the first portion of the mid-srut, and sometimes also into the stomach-like enlaro:ement. The numbei', as well as the relative size of the separate portions of the liver, varies greatly. As a rule, however, when the liver increases in size it becomes less complex, while the smaller the lobes the more numerous they are. This mode of arrangement along a large portion of the enteric canal leads to certain changes in this portion of the enteron in one division of the Opisthobranchiata. The ducts of the several lobes of the liver widen out, and so form diverticula of the stomach; when, therefore, there are a large number of hepatic tubes opening into the stomach, its inner surface has a reticular appear- ance (Doris, Doridopsis). Owing to this change, which is easily explicable by a reference to the origin of the liver, the glandular portion of this organ becomes apparently a mere covering for these irregular diverticula. This is indeed the origin of that arrangement of the digestive system in the JEolidifB and others, to which we have already called attention (§ 278). The liver has the form of wide ctecal appendages, which arise from the mid- gut (Fig. 194, m), or so-called stomach. They are either directly connected, when the appendages open at once into the mid-gut, or indirectly, when they still form wide diverticula of it (Fig. 194); and these, too, may be due to certain changes in a part of the liver. These appendages traverse the coelom and send blind processes into the dorsal cirri, when such are present. These processes are
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