Echinoderms of Connecticut (1912) Echinoderms of Connecticut echinodermsofcon00coew Year: 1912 No. 19.] ECHINODERMS OF CONNECTICUT. 103 symmetrical, with both mouth and anus, and is known as a pluteus (Fig. 16). It bears absolutely no resemblance to the adult urchin. The free-swimming pluteus lives and feeds at the sur- face for a period of several weeks, the time depending some- what on the temperature and other conditions, and varying in different species. In this time it may have been carried by cur- rents and tides to a considerable distance from its place of origin. FIG. 17. Arbacia pu
Echinoderms of Connecticut (1912) Echinoderms of Connecticut echinodermsofcon00coew Year: 1912 No. 19.] ECHINODERMS OF CONNECTICUT. 103 symmetrical, with both mouth and anus, and is known as a pluteus (Fig. 16). It bears absolutely no resemblance to the adult urchin. The free-swimming pluteus lives and feeds at the sur- face for a period of several weeks, the time depending some- what on the temperature and other conditions, and varying in different species. In this time it may have been carried by cur- rents and tides to a considerable distance from its place of origin. FIG. 17. Arbacia punctulata. Side view of young urchin immediately after the metamorphosis. The spines re- maining from the pluteus are in process of absorption. (After Brooks^.) When ready to assume the adult form, the pluteus settles to the bottom, absorbs its larval organs, and by a complicated meta- morphosis assumes the condition of a young urchin (Figs. 17 and 18). The young urchin differs from the adult in having the whole upper surface covered by the plates which will event- ually form only the periproct of the adult, and by the relatively enormous tube-feet. The animal is now radially .symmetrical, and creeps about on the sea bottom after the manner of the adult urchin. It feeds upon diatoms and other minute organisms until,
Size: 1289px × 1551px
Photo credit: © Bookworm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
