. Elements of comparative anatomy. Anatomy, Comparative. Fi°\ 168. Lateral view of the mantle-cavity of a Mactra; the right mantle-lamella has been removed. br br' Branchia?. t Tentacle, ta tr Siphons. mp Posterior adductor, p Foot, c Umbo. 5)ia Anterior, separate portions of the mantle; or there may be a respiratory tube, which is siuo-lo externally, and is only divided internally into two canals by a partition; or the two conditions may be combined (Fio\ 1G8, tr ta); or, finally, two completely separate tubes may be developed : an upper one, the inner orifice of which is opposite the anus, a
. Elements of comparative anatomy. Anatomy, Comparative. Fi°\ 168. Lateral view of the mantle-cavity of a Mactra; the right mantle-lamella has been removed. br br' Branchia?. t Tentacle, ta tr Siphons. mp Posterior adductor, p Foot, c Umbo. 5)ia Anterior, separate portions of the mantle; or there may be a respiratory tube, which is siuo-lo externally, and is only divided internally into two canals by a partition; or the two conditions may be combined (Fio\ 1G8, tr ta); or, finally, two completely separate tubes may be developed : an upper one, the inner orifice of which is opposite the anus, and serves for the exit of the water, and a lower one, by which the water passes in. The investment of cilia causes the two streams to pass regularly in and out. Through these forms we arc led up to those in which the respiratory cavity is most completely closed, and the pallial tubes most developed. This is accom- panied by a diminution in the size of the cleft in the mantle through which the foot is protruded. This has become much narrower, and is placed some way from the respiratory tubes, so that the greater part of the edges of the mantle have grown together, in consequence of which the body of the animal is sac-like (Boring Mollusca). The orifice of passage for the foot is now placed at the anterior end, and tli e. / P The same animal with its foot and siphons re- tracted, ins Siphonal muscle. Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gegenbaur, C. (Carl), 1826-1903; Bell, F. J. (Francis Jeffrey), 1855-1924; Lankester, E. Ray (Edwin Ray), Sir, 1847-1929. London, Macmillan and Co.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
