Action of Salt Solutions upon Eggs
Action of Salt Solutions upon Eggs. -Few now underrate the value of physiological experimentation as an aid in the advance of pure science as well as a basis for practical arts, even though the results obtained may be but abnormal states of the organisms studied; it is a hopeful sign of the times that these methods are being so actively extended to the study of the lowest organisms and even to the sphinx-like mystery of the egg. An important venture in this direction is that of Professor T. H.
... of Professor T. H. Morgan,' who now adds a second paper to his first account of notable discoveries published three years ago. This paper contains the results of arduous labor, and is illustrated by careful drawings. Only a few of the many important facts and inferences can be touched upon here. The author found that sea-urchin eggs, whether fertilized or not, when placed a short time in sea water to which two per cent or less of sodium or magnesium chloride has been added, and then returned to common sea water, show inside clear spots which change position and number. When these eggs are sectioned and stained, the clear spots are represented by darkly stained regions and radiating lines in fact "stars" comparable to those seen in karyokinesis. Some stars have central specks comparable to centrosomes. If the eggs are not fertilized, they may nevertheless, when so treated, undergo a process of cleavage into many cells. The cleavage, however, is not like the normal, nor does it lead to the formation of larvae, so far as known. Sections of such eggs show that the chromosomes are distributed through the egg, apparently by the action of the stars, and that the cleavage of the egg takes place about these chromosomes as centers. * In some other animals, notably a Nemertean and a Gephyrean, similar star-formations were produced by treating the unfertilized eggs with the same salt solutions. It is thus possible to bring out stars and centrosomes similar to the normal ones, but in abnormal numbers and positions, by mere Arc/hivf. Enlwicklungsmechatnik, i899, Ed. viii, pp. 448-536, PIs. VI-X.