. The doctrine of descent and Darwinism. Evolution. TYPES AND FAMILIES. 31 arranged radially round an axis, passing through the dor- sal and ventral pole. The cavity, which in most other ani- mals—for instance, in man—is termed the abdominal cavity, the space between the intestinal wall and the abdominal parietes, is deficient in them; but, on the other hand, from the stomach proceed in general vari- ous kinds-of tubes and branchia, which to a certain ex- tent replace the abdominal cavity. Fig. 2 represents a. Medusa, Tiaropsis Diadema, after Agassiz. The darkly- shaded organs form the so-call

- Image ID: RDJ5RC
. The doctrine of descent and Darwinism. Evolution. TYPES AND FAMILIES. 31 arranged radially round an axis, passing through the dor- sal and ventral pole. The cavity, which in most other ani- mals—for instance, in man—is termed the abdominal cavity, the space between the intestinal wall and the abdominal parietes, is deficient in them; but, on the other hand, from the stomach proceed in general vari- ous kinds-of tubes and branchia, which to a certain ex- tent replace the abdominal cavity. Fig. 2 represents a. Medusa, Tiaropsis Diadema, after Agassiz. The darkly- shaded organs form the so-call
The Book Worm / Alamy Stock Photo
Image ID: RDJ5RC
. The doctrine of descent and Darwinism. Evolution. TYPES AND FAMILIES. 31 arranged radially round an axis, passing through the dor- sal and ventral pole. The cavity, which in most other ani- mals—for instance, in man—is termed the abdominal cavity, the space between the intestinal wall and the abdominal parietes, is deficient in them; but, on the other hand, from the stomach proceed in general vari- ous kinds-of tubes and branchia, which to a certain ex- tent replace the abdominal cavity. Fig. 2 represents a. Medusa, Tiaropsis Diadema, after Agassiz. The darkly- shaded organs form the so-called coelenteric apparatus. Of the Echinoderms, the reader is probably ac- quainted, at least with the star-fish (Asterias) and the sea-urchin (Echinus), of which the general form is like- wise usually radiate. Besides a peculiar chalky deposit, or greater or less calcification of the skin covering, a system of water-canals forms a characteristic of this family. With these are connected the rows of suckers, which, by protrusion and retraction, serve as organs of locomotion. On account of the radiate structure pre- vailing among the Echinoderms, Medusae, and Polypes,. 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 work.. Schmidt, Dr. (Eduard Oskar), 1823-1886. New York, Appleton

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