The Lansing Effect, simply stated, is that the offspring of old parents tend to have shorter lifespans than the offspring of young parents and in both cases these tendencies are transmitted to successive generations . This statement is difficult to justify from Lansing's data because of the variation in mean lifespan that was observed from one generation to the next . A more precise statement of the Lansing Effect is that isogenic lines derived from young parents tend to persist for more generations than lines derived from old parents .
Lansing considered aging to be the result of a factor that was transmitted from mother to offspring via the eggs . He proposed that this factor influences longevity and also alters the pattern of reproduction . Members of short-lived lines derived from old parents reproduced earlier and at higher rates in succeeding generations . In contrast, members of long-lived lines derived from young parents delayed initial reproduction to later age classes in succeeding generations . These proposals are examined using a life table analysis of Lansing's data . The results suggest that the Lansing Effect in Philodina citrina is not due to aging, but rather is the direct result of the changes in fecundity patterns . Accordingly, it would seem prudent to regard the Lansing Effect with some skepticism until more is known about its physiological basis .