. Zoology for high schools and colleges. Zoology. AWATOMY OF THE CLAM. 325 to the heart; one end is secretory, lamellar and glandular, communicating with the pericardial cavity, while the other is excretory and opens into the cavity of the gill. The. nervous system can be, with care and patience, worked out in the clam or fresh-water mussel. In the clam {Mya arena-. vis- Circnlatory system of Anodonta, a fresh-water mussel, after Bojanns. 1. ventricle; 2, arterial system ; 14 and 15, veins which follow the border of the mantle. The veins lead the blood in part directly towards the organ
. Zoology for high schools and colleges. Zoology. AWATOMY OF THE CLAM. 325 to the heart; one end is secretory, lamellar and glandular, communicating with the pericardial cavity, while the other is excretory and opens into the cavity of the gill. The. nervous system can be, with care and patience, worked out in the clam or fresh-water mussel. In the clam {Mya arena-. vis- Circnlatory system of Anodonta, a fresh-water mussel, after Bojanns. 1. ventricle; 2, arterial system ; 14 and 15, veins which follow the border of the mantle. The veins lead the blood in part directly towards the organ 4, which is the iidney or "organ of Bojanus," and in part to the venous sinus of the upper surface of this organ ; 5, veins which carry back the blood from the gills, the rest going to the sinus, 6, where arise the branchial arteries; 7, 8, the branchial veins, and 9, the gill.—From Gervais et Van Beneden. ria. Fig. 159) it consists of three pairs of small ganglia, one above (the "brain") and one below the oesophagus (the pedal ganglia) connected by a commissure, thus forming an oesophageal ring; and at the middle of the mantle, near the base of the gills, is a third pair of ganglia (parieto-splanch- nic), from which nerves are sent to the gills and to each division of the siphon. This last pair of ganglia can be usually found with ease, without dissection, especially after the clam has been hardened in alcohol. The ear of the clam is situated in the so-called foot; it bears the name of otocyst (Fig. 160, i), and is connected with a nerve sent off from the pedal ganglion. It is a little white body found by laying open the fleshy foot through the middle. Microscopic ex- amination shows that it is a sac lined by an epithelium, rest- mg on a thin ner\'ous layer supported by an external coat of connective tissue. From the epithelium spring long hairs; the sac contains fluid and a large otolith. The structure of this octocyst may be considered typical for Inver
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishe, booksubjectzoology
