Boss, K. J. 1974. Oblomovism in the Mollusca. Trans. Amer. Micros. Soc., 93: 460-481. Molluscs have two major dormant stages: hibernation, a reaction to reduced temperatures; and aestivation, a response to extremes of heat and drought. These behaviors are collectively referred to as Oblomovism, a term descriptive of the retiring existence recounted by the Russian Goncharov in his novel Oblomov. Certain species exhibit a phenomenal capacity for survival in inhospitable environments by remaining in a sustained dormant state for up to five or six years, and sometimes more. The best documentation of molluscan Oblomovism occurs among marine prosobranch snails, fresh-water bivalves, and fresh-water and terrestrial gastropods, both prosobranch and pulmonate. The evidence suggests that basommatophoran and stylommatophoran pulmonates are better able to tolerate greater environmental extremes than are prosobranchs, a generalization supported by zoogeography. It is postulated that the capability of conquering the exigencies of physically rigorous environments plays an important role in the expansion of geographic ranges of species and may have profound consequences on the processes of speciation and extinction.