THE TORTUGAS LABORATORY 4°7 



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 ap- 

 pears to be an analogy between the mode of growth of cancer and re- 

 generation. Possibly, then, if we could control regeneration some simi- 

 lar 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 Ilipponoe and Toxop- 

 neustes, 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 Hipponoe 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 condi- 

 tions 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. Daven- 

 port 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 upo^ 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 pos- 

 terior 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. Pro- 

 fessor 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 swarm- 

 ing reaction. Previous studies at Tortugas have shown that the 



