The Effects of Dehydration upon the Hatchability of Limax Flavus Eggs

Abstract

While one of us (E. B. C., '31) was investigating the action of ultraviolet rays on the embryos of Lintax flavus Linnaeus, it was noticed that some batches of eggs were so dehydrated that they were wrinkled or had depressions in them. This condition prevailed if the eggs were laid in a dry or moderately damp receptacle. These eggs, however, would hatch if placed in a moist container. Khalil ('22) found that Planorbis corners were quite susceptible to drying, being killed in five hours when in a jelly-like mass. Adolph and Adolph ('25) placed Lumbricus terrestris in a 0.I36 M solution of sodium chloride for twenty hours and found that the worms would recover after a 35 per cent loss in weight. Jackson ('26) also, working on Lumbricus terrestris. found that they would live, after losing 43 per cent of their original weight in four to five hours, when placed on dry filter paper. Jackson found that they would die if they lost 50 to 6o per cent of their weight. Since the eggs of Limnax flavus Linnaeus hatched after being dehydrated enough to show a definite depression, we decided to perform a series of experiments to determine the maximum loss in weight which the young would survive and still be able to hatch. The eggs are fastened together by means of a membrane and thus all are laid at once. The slugs do not move while laying; hence the eggs become superimposed and are able to retain their moisture for a longer period than single eggs. The eggs varied considerably in weight: the maximum being 97.49 milligrams and the minimum being 5I.i6 milligrams. The average weight for I,200 eggs was found to be 78.7I milligrams. The eggs are elliptical in shape, the average diameter being about 0.5 centimeter and the average length being about 0.75 centimeter. They are covered with a rather tough membrane, which allows them to be moved on dry filter paper without being ruptured. A vitilline membrane surrounds the embryo, and this membrane is surrounded by a semi-fluid gelatinous mass, which resembles egg white. These experiments were conducted at room temperature (20 to 300 C.). The slug eggs, containing embryos from one to twenty-two days old, were weighed and subjected to dehydration. The eggs were placed on clean dry filter paper, the drying process lasting from two to seven hours. The eggs were weighed at the end of definite periods and placed in Petri dishes on moist filter paper. The weights given in this paper are averages in all cases.