THE TORTUGAS LABORATORY 409 



the most accurate and extensive investigation of the associations, habits, 

 rate of growth and constitution of corals ever attempted by any natural- 

 ist. 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 condi- 

 tions 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 cen- 

 tral 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 nourish- 

 ment. Thus animals so low as the jellyfishes show the beginning of 

 that differentiation of organ-forming substances in tne egg which Pro- 

 fessor 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 His- 

 tory, 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 Mu- 

 seum 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, 



VOL. LXXVI. — 28. 



