. The infancy of animals. Animals. Compare the larvae, for instance, of such sedentary animals as the oyster, that extraordinarily interesting shell-fish known as Yoldia—a near relation of the Razor- shell, and one of the most ancient types of moUusca now living, its for- bears being trace- able into the remote geological past— and the infant stages of the two fresh-water mussels Driessensia and Anodonta. These are all different, as their parents are different, but all are for a time free- swimming. Sooner or later, however, they have to settle down in life, grow a pair of shells, and become r
. The infancy of animals. Animals. Compare the larvae, for instance, of such sedentary animals as the oyster, that extraordinarily interesting shell-fish known as Yoldia—a near relation of the Razor- shell, and one of the most ancient types of moUusca now living, its for- bears being trace- able into the remote geological past— and the infant stages of the two fresh-water mussels Driessensia and Anodonta. These are all different, as their parents are different, but all are for a time free- swimming. Sooner or later, however, they have to settle down in life, grow a pair of shells, and become respectable. But of these the little anodonta has by far the most ad- venturous existence. For a time it shelters within its parent's gills, but on the first favourable opportunity it is suddenly expelled, with a swarm of its brothers and sisters, to the number of half a million or more at once ! This is freedom,. YOUNG MOLLUSCA. A shows the larval state of Yoldia, a near relation of the Razor-shell. B and C show the free-swimming, larval stage of the Oyster. D and E are Glochidia—the larvse of the fresh- water mussels Anodonta. Note the teeth on the shell, and the long, vibratile " ;. 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 Pycraft, W. P. , (William Plane), b. 1868. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanimals, bookyear1913
