Page:Popular Science Monthly Volume 57.djvu/234

224 the egg, is incited by chemical stimulus; and several observers before Loeb had shown that when unfertilized seaurchin eggs are treated by the addition to the sea-water of various substances, such as strychnine or chlorides of sodium or magnesium, they may undergo some of the preliminary changes of development and may even segment. Loeb was able to induce complete and normal development by first bringing the eggs for about two hours into a mixture of sea-water and a weak solution of magnesium chloride, and then transferring them to normal sea-water. Eggs thus treated segmented and underwent a development which, though somewhat slower than usual, was otherwise normal and produced perfect larvæ. This effect can not properly be called fertilization in the ordinary sense of the word, but is rather to be regarded as artificially induced parthenogenesis. It points unmistakably, however, to the possibility, or rather probability, that in normal fertilization the spermatozoon incites the egg to development by bringing to it certain definite chemical substances; and Loeb gives reasons for the view that these substances are probably in the form of ions, concluding that these and not the nucleins are essential to the process of fertilization. A highly suggestive new field for work is opened by these experiments.

can not bring the phenomena they study into the laboratory or test the behavior of the heavenly bodies under artificial conditions. They have to be satisfied with such opportunities as nature gives, even though she bestows them as meagerly as she does solar eclipses. Consequently, the total eclipse of the forenoon of May 28th has been the object of much preparation. Most of the important astronomical observatories in this country will have parties stationed along the path of the eclipse from New Orleans to Norfolk, Va. Many European parties will observe the eclipse in Portugal, Spain and North Africa. It has been pointed out by Prof. R. W. Wood and Mr. A. L. Rotch that there are several important physical observations to be made apart from the astronomical observations on the sun's corona described by Professor Bigelow, in the May number of this magazine. Just before and after totality alternate bright and dark bands are observed sweeping across the country. It is hoped that by the coöperation of a number of observers more complete and exact data concerning this phenomena may be gathered and its explanation found. The changes in the wind noted during eclipses will also be observed to ascertain whether the sudden cooling of the atmosphere by the passage of the moon's shadow is a sufficient explanation of the so-called 'eclipse wind.' Those who know nothing about theories of the corona or of the 'eclipse wind' will be interested in the more obvious phenomena and in some cases, in the opportunity to take such a photograph as can not be duplicated in this country until 1918. The most favored ones are those who live in the fifty-mile belt of the total eclipse, but the sun will be seen nine tenths covered in the eastern and southern States, and will be six tenths covered to those in the least favorable locality of the United States, the extreme northwest. The proper methods of observing and photographing the corona were described in Professor Bigelow's article on the eclipse in the May number of the