The Effects of Continued Exposure to Moisture on the Weights of Fertile and Non‐Fertile Eggs of the Slug, Limax Flavus L.

Abstract

Eggs of the slug, Limax flavus Linnaeus, lost weight very rapidly when placed on dry filter paper (Carmichael and Rivers, '32). The eggs were covered with a membrane which allowed this exchange of moisture. Since this membrane was not rigid it was decided to determine whether the weights of the eggs would remain the same until the time of hatching if they were allowed to be in contact with moist filter paper. Hayes ('30) found that the wet weight of salmon eggs increases slowly until a short time before hatching and then rapidly. The slug eggs were laid in the laboratory. After being separated and washed, they were placed on moist filter paper until they regained any weight which they had lost either during the time required for laying or in the case of those that were laid during the night, until they were observed the next day. Tap water was used for washing and for moistening the filter paper. The different batches of eggs were left on the moist filter paper for varied lengths of time previous to the first weighing, but the periods were always of several hours duration. The eggs, when laid, were fastened together by a connecting membrane and thus necessitated being separated before starting the experiment. After a few hours of preliminary moistening, the eggs were placed on dry filter paper for about thirty seconds in order to remove the external moisture. The eggs were weighed and placed back on moist filter paper. The above process of weighing was repeated at intervals of a day or more up to the time of hatching. Non-fertile eggs, as controls, were carried through the above procedures. Figure 1 illustrates the effects on the weights of fertile and non-fertile slug eggs which have remained in contact with moist filter paper. The data are averages of the weights of the eggs in whole batches and a single curve represents effects on one batch. The curves in figure 1 are given as representative ones of the several batches which have been observed. Several of the curves are somewhat irregular during the first few days of the experiment. There was a marked increase in the weight of the fertile eggs after about the eighth day, figure 1, A. This increase was accelerated until the eggs reached a maximum weight which occurred in most cases between the fifteenth and eighteenth days after being laid. Then there was usually a rapid loss in weight until the hatching began. When a majority of the eggs in a batch had hatched, the weighings were discontinued. As controls, non-fertile eggs were allowed to remain on moist filter paper for definite periods which correspond to the time required for hatching of fertile eggs, figure 1, B. The increases in the weights of the non-fertile eggs in 15 to 18 days were never as great as they were in the case of the fertile eggs. That the weights of most of the batches of control eggs given here are not the maximum weights that could have been attained is fairly certain since a majority of the curves show that the eggs were increasing in weight at the time these particular experiments were discontinued.