. A textbook in general zoology. Zoology. 94 STARFISH, SEA URCHIN, BRITTLE STARS ijy eggs ami the sexes are separate. The ovaries of the female are within the body ca\dt}- at the bases of the arms. There is one pair for each arm. The spermaries of the male are in a similar situation. When the ova are mature, they are extruded into the sea through small pores in the body ^^â alls at the bases of the arms. In the sea they are fertilized by the sperms and finally hatch into forms very different from the adults. It is also an interesting fact that the young are bilaterally symmetrical. The young f
. A textbook in general zoology. Zoology. 94 STARFISH, SEA URCHIN, BRITTLE STARS ijy eggs ami the sexes are separate. The ovaries of the female are within the body ca\dt}- at the bases of the arms. There is one pair for each arm. The spermaries of the male are in a similar situation. When the ova are mature, they are extruded into the sea through small pores in the body ^^â alls at the bases of the arms. In the sea they are fertilized by the sperms and finally hatch into forms very different from the adults. It is also an interesting fact that the young are bilaterally symmetrical. The young feed on microscopic organisms and, as they grow, imdergo radical changes imtil finally they assume the form of the parent starfish. Other Echinoderms Not all starfish have just five arms. Indeed, abnormal specimens of the common starfish are sometimes fomid with four or six arms. But there are some species that normally have more than five arms. One species has as many as thirty. Again, the members of one genus have six arms, an irregular munber. Xot all starfish are like the one described in regard to the central disk. In some, the disk is more plainly marked off and is more distinct, while in others the spaces between the arms are filled up nearly. Fig. 46. â Ventral surface of a kind of star- fish in which the cUsk extends much farther out than in tire common 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 Herrick, Glenn W. (Glenn Washington), 1870-1965. New York, Cincinnati [etc. ] American Book Company
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