XXI.—The Life-history and Development of Agriolimax agrestis L., the Gray Field Slug.

Abstract

Among Gasteropod Molluscs the life-histories and development of the most highly evolved members, the terrestrial Pulmonates, have been less intensively studied than those of more primitive aquatic forms. This has been due in part to the technical difficulties involved in the permanent preparation of material for study, and in part to the fact that the investigator seeking for primitive features of phyletic interest is more likely to find these among more generalised species of Gasteropods than among those which are obviously adapted, both during the early stages of their development and in adult life, to a habitat far removed from the ancestral one.It is the purpose of this paper to present data bearing upon the life-history of a single species of land Pulmonate, Agriolimax agrestis L., to enlarge upon certain aspects of the embryology of this species, and to demonstrate the structural and functional changes of the larva which have accompanied the transition from an aquatic to a terrestrial breeding habit.