THE REACTIONS OF CERTAIN ANIMALS TO GRADIENTS OF EVAPORATING POWER OF AIR. A STUDY IN EXPERIMENTAL ECOLOGY

Abstract

1. Nereis eggs, inseminated with sperm cells which have been injured by one of several methods, may fail to develop in a normal manner. 2. In some cases the egg does not form a fertilization cone, attachment granules are lacking and the sperm head is not drawn into the egg but remains outside attached to the vitelline membrane. There are two classes of such eggs, neither of which segment, viz.: (a) Those which slowly undergo maturation without forming jelly. (b) Those which form both jelly and polar bodies. 3. Those eggs in which the sperm head enters, form the first cleavage spindle in an apparently normal fashion but may fail to complete the division of the cytoplasm. Those which complete this division may develop abnormalities in later stages. 4. The eggs of Arbacia exhibit a similar series of abnormalities when fertilized by weakened sperm cells. 5. There is no indication of specificity in the action of the agents used in injuring the sperm cells. 6. These experjments demonstrate that eggs fertilized with sperm cells injured by alcohol and by other means may produce abnormal forms. Taken in connection with the demonstration by others that the germ cells of mammals may be exposed to injurious conditions this has an important bearing upon the relation of alcoholism to the production of defectives. 7. There seem to be at least two factors involved in the process of fertilization. The one has to do with membrane formation and certain other changes, the other with the internal stimulus. 8. In Nereis the presence of the two germ nuclei within the egg is not necessarily sufficient as an internal stimulus for normal development.