Page:Popular Science Monthly Volume 76.djvu/413

Rh the most accurate and extensive investigation of the associations, habits, rate of growth and constitution of corals ever attempted by any naturalist. He is rearing corals from the free-swimming larva, and observing their rate of growth as well as studying the growth-rate of many coral beads found living upon the reefs or in the moat of Fort Jefferson. Years must elapse before the results of these studies will be ready for publication, but he has already discovered that under favorable conditions the rate of growth of corals is surprisingly rapid, and that the free-swimming stage of the planula lasts long enough for corals to be drifted fully 800 miles by the Gulf Stream.

Professor Edwin G. Conklin, of Princeton, finds that the egg of the scyphomedusa Linerges consists of an outer layer of clear protoplasm, an intermediate shell of densely packed yolk spherules and a central sphere of dissolved yolk. The outer layer of the egg forms the peripheral layer of the gastrula and blastula, and gives rise to the cilia of the ectoderm. The middle layer constitutes the principal part of all of the cells of the body, while the central yolk serves for nourishment. Thus animals so low as the jellyfishes show the beginning of that differentiation of organ-forming substances in the egg which Professor Conklin discovered was so characteristic of the eggs of higher forms. He also finds that the gastrula larva in this medusa may be formed either by invagination or by unipolar ingression, thus showing the intimate relationship between these apparently distinct processes.

Dr. E. P. Cowles, of Johns Hopkins, carried out an extensive series of observations upon the habits and reactions of the ghost crab Ocypoda arcnaria, which lives upon the sandy beaches of the Tortugas. It will be impossible to do more than present a few of his most important results. He finds that this crab can not detect color, but is sensitive to large differences in the intensity of light, and it readily perceives a moving object. The color pattern of the crab changes under different conditions of light and temperature, becoming dark and mottled in dull light and low temperature. It can not detect sound waves traveling through air, but its so-called "auditory organs" are actually organs of equilibration. The crab has memory, is able to profit by experience and can form habits.

Dr. Prank M. Chapman, of the American Museum of Natural History, discovered that the booby, Sula fiba, which nests upon Cay Verde, Bahamas, between February and April, lays two eggs but rears only one young bird. His observations and collections upon Cay Verde has led to the construction of a very attractive group in the American Museum of Natural History in New York illustrating the nesting habits of the frigate-bird and the booby.

Pleasurable as the task would be, limitations of space prohibit my reviewing the results of the studies of Messrs. Brooks, Hartmeyer,