Page:Popular Science Monthly Volume 76.djvu/411

Rh and the animal acquires two equally developed small claws at the next molt. Thus a tendency toward a reversal is checked.

In another research, Dr. Stockard made the interesting observation that when a piece of a jellyfish (Cassiopea) is cut away and the animal starved a new piece regenerates, even though the old part of the body shrinks in size to provide it nutriment. Cancers also grow in this manner at the expense of the surrounding tissues, and thus there appears to be an analogy between the mode of growth of cancer and regeneration. Possibly, then, if we could control regeneration some similar process might be found effective to check the growth of cancer.

As is now well known to naturalists, Tower has succeeded through the influence of heat and moisture in producing a new sort of beetle which breeds true as would a newly arisen species. MacDougal has also succeeded through chemical means in effecting the same result with plants. Recently, at Tortugas, Professor Tennent, of Bryn Mawr, produced hybrids by reciprocal crosses between Hipponoë and Toxopneustes, two common sea-urchins of the reefs; and he discovered the interesting fact that if the sea-water be normal or rendered alkaline the larvae resemble the Hipponæ parent, but if the sea-water be treated with an acid so as to reduce its alkalinity the larva? resembled their Toxopneustes parent. .He could then by changing the external conditions produce larva? resembling either parent he choose, and thus alter the dominance of either parent at will.

No one knew what caused the newly hatched young of the great sea-turtles to crawl toward the ocean as soon as they had dug their way upward out of the sand within which their eggs are laid, but Dr. Davenport Hooker, of Yale, found that the young turtle is attracted toward the ocean by the blue color of the water. If it sees the ocean through red, yellow or green glass it does not crawl toward it, but if a piece of blue glass, or even blue paper, be placed anywhere within range of its vision the turtle at once scuttles toward it with great excitement.

If one goes out upon the ocean before sunrise on the morning of a day within three days of the time of the last quarter of the July moon, the surface will be found to be covered with actively wriggling worms, about six inches long, swimming in all directions. These are the posterior ends of the Atlantic palolo worm (Eunice fucata) which breaks off from the head end of the animal and swims upward from the crevices of the coral reef, to take part in the breeding swarm. Professor Aaron L. Treadwell, of Vassar College, is now studying this phenomenon, and he has discovered that if the rocks containing the worms be placed in a dark chamber upon the day preceding the night of the swarm the worms may still swarm. Hence, contrary to Mayer's supposition, the presence of moonlight is not necessary for the swarming reaction. Previous studies at Tortugas have shown that the