MOLLUSCA. 819 



margins, like a rolled leaf, free beneath, which are thrown one over 

 the other ; in the other Cephalopods it opens at the anterior extremity 

 alone. Below, this funnel passes into the cavity within which the 

 gills are situated, and into which the terminations of the sexual 

 organs and of the intestinal canal open. The contraction of the 

 funnel forces out the water at its opening below the head. Before 

 the opening there is usually placed a valvular organ (not unlike an 

 epiglottis), by which the reflux of the water is prevented. 



The mouth lies in the middle between the arms, surrounded by a 

 circular fold of skin. Here are seen two large, curved, horny jaws, 

 which resemble in some degree the bill of a parrot, and of which the 

 lower overlaps the upper and smaller. Between the jaws is placed 

 a membranous tongue, which is soft at the point and beset with 

 papillae, but elsewhere is covered with hard, horny plates and 

 spines. In the sac of the mantle most of the viscera (with exception 

 of the gills) are situated in a proper cavity, which is distinct from 

 that of the gills that opens externally through the funnel. 



The respiratory organs are two or four gills, which, pointed coni- 

 cally, run obliquely upwards, and are situated, one or two on each 

 side, in the base of the sac, which terminates in the funnel. They 

 are affixed here to a fleshy, projecting margin, and consist of mem- 

 branous leaflets, incised at the edge, each of which is affixed by a 

 separate stalk to the projecting margin. In those that have only 

 two gills, a venous heart is situated at the base of each of these; in 

 the Nautilus, that has four gills, these two venous hearts are not 

 present. On the large venous stems which conduct the venous 

 blood towards the gills, spongy appendages, usually of a brown- 

 yellow colour, united in bundles, and sometimes subdivided blind 

 folliculi, which we noticed above (p. 760) as kidneys, are situated. 

 The cavities in which these veins lie, are washed by water that has a 

 free access to them through special apertures in the branchial cavity. 



The sexual organs, in both sexes, are situated in the base or pos- 

 terior extremity of the visceral sac. The ovarium is in all single, 

 although in many two oviducts are present, which then, however, 

 arise from a short common canal. This ovary consists of a sac with 

 thick walls, on the inside of which, the eggs inclosed in proper cap- 

 sules, are affixed by pedicles. For the secretion of the envelop of 

 the eggs there is a glandular organ, which in Octopus surrounds each 

 oviduct, or the walls of the oviduct itself are thickened towards the 

 extremity by a glandular tissue which supplies the same secretion. 

 One or two glands composed of many laminae, which however are 



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