Analysis of the Activity of the Fresh‐Water Snail, Viviparus Malleatus (Reeve)

Analyses of the activity of animal species indicate that, within a given community, there is activity on the part of the several species comprising the community resulting in complete occupation of the twenty-four hour or diel cycle. Diurnal species are active during the lighted portion of the diel cycle; nocturnal species are active during the darkened portion; other species may be active during both the lighted and darkened portion. The activity of certain species is periodically repetitive or rhythmic with respect to the diel cycle; in some of these species this rhythmicity has been demonstrated to be exogenous or developed as a result of the rhythmicity of the environment, while in others it has been demonstrated to be endogenous or inherent. The activity of other species in the community presents no regularly repetitive group action and has been described as arhythmic or aperiodic. The subject of species population activity within the community has been treated comprehensively by Park ('40). The activity of the species populations comprising the aquatic communities has been less frequently analyzed than that of populations comprising the terrestrial communities. The vertical migration of plankton in the pelagic zone has received considerable attention (Juday, '03, '21; Birge and Juday, '11; Russell, '27; Nicholls, '33; Welch, '35; Clarke, '39; Tressler, '39), and the rhythmicity of this community has been established. However, whether this rhythmicity is endogenous or exogenous, that is, persistent and unaffected by experimentally altering environmental conditions, or distinctly controlled by fluctuating environmental conditions, remains to be demonstrated by mechanically controlled experimental analyses. The works of several investigators (Esterly, '17; Ederstrom, '39) are steps in this direction. Investigation of the nekton organisms of the pelagic region has only begun with the designing of recording apparatus for small fish being accomplished by Spencer ('29) and Spoor ('41), and the recording of the activity of certain fresh-water fishes by Spencer ('39). Concerning the activity of the littoral community, Polimanti ('11) observed the periods of rest and activity of many marine invertebrates, but actual analysis of the activity of these forms under controlled conditions was not undertaken. More recently, Parker ('32) observed that certain Arbacias capture food by night, and Stier ('33) investigated an interesting periodism in the number of locomotor waves of the sea cucumber, Thyone briareus. Moon ('40), in studies on the rate at which certain flooded littoral areas were populated, observed that many species inhabiting this area were nocturnal, a few diurnal, and one arhythmic. The controlled investigation by Roberts ('36) established the rhythmic activity of the common crayfish, Cambarus virilis. The arhythmic activity of