This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1893 Excerpt: ...intestine; in the articulate brachiopods the latter is short and ends blindly, in the inarticulate it is long and ends in an anus which opens into the pallial chamber. The nervous system consists of a ring round the cesophagus, with ganglionic enlargements from which nerves are given off to the arms, mantle, etc. The ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1893 Excerpt: ...intestine; in the articulate brachiopods the latter is short and ends blindly, in the inarticulate it is long and ends in an anus which opens into the pallial chamber. The nervous system consists of a ring round the cesophagus, with ganglionic enlargements from which nerves are given off to the arms, mantle, etc. The part of the body-cavity which surrounds the alimentary canal communicates with the pallial chamber by means of two or four funnel-shaped canals. The body-cavity extends into the mantle as a series of spaces or sinuses; these produce slight depressions on the interior of the valves, and can often be traced in casts of the interior of fossil specimens as ridges (fig. 40). The body-cavity is filled with a fluid which is kept in motion by means of cilia. A heart appears to be absent, but a vesicle on the dorsal surface of the stomach has been described as such. L The brachiopods are never colonial animals. Reproduction takes place sexually, never by budding or fission. The genital organs are placed in the body-cavity, in the sinuses of the mantle, or in both. Some forms are hermaphrodite, others diceceous. The greater part of the pallial chamber is occupied by two long processes, the arms (fig. 29, d), given off from the sides of the mouth. These are covered with cirri (h), and they, with the mantle serve as organs of respiration. The cirri also produce a current of water, which carries food to the mouth. Of the two valves of the brachiopod, the ventral is always larger than the dorsal, and it is produced into a beak or umbone, the termination of which is generally perforated by a foramen (fig. 32 A, /). Each valve is equilateral, that is to say, a line drawn from the umbone to the opposite margin of the shell divides the valves into two equal and ...
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