Fig. 67.—Crinoid, arms closed.
Fig. 68.—Disk of Crinoid from above, showing mouth in centre and vent near it, at right (arms removed).
The crinoids are the most ancient of the echinoderms. (Figs. [67], [68].) Their fossils are very abundant in the rocks. They inhabited the geological seas, and it is believed that some of the other echinoderms descended from them. A few now inhabit the deep seas. Some species are fixed by stems when young, and later break away and become free-swimming, others remain fixed throughout life.
The four classes of the branch echinoderms are Starfish (asteroids), Sea urchins (echinoids), Sea cucumbers (holothurians), and Sea lilies (crinoids).
Comparative Review
Make a table like this as large as the page of the notebook will allow, and fill in without guessing.
| Amœba | Sponge | Hydra | Coral Polyp | Starfish | |
|---|---|---|---|---|---|
| Is body round, two-sided, or irregular | |||||
| What organs of sense | |||||
| Openings into body | |||||
| Hard or supporting | |||||
| parts of body | |||||
| How food is taken | |||||
| How move | |||||
| How breathe |
CHAPTER VI
WORMS
Suggestions:—Earthworms may be found in the daytime after a heavy rain, or by digging or turning over planks, logs, etc., in damp places. They may be found on the surface at night by searching with a lantern. Live specimens may be kept in the laboratory in a box packed with damp (not wet) loam and dead leaves. They may be fed on bits of fat meat, cabbage, onion, etc., dropped on the surface. When studying live worms, they should be allowed to crawl on damp paper or wood. An earthworm placed in a glass tube with rich, damp soil, may be watched from day to day.