OBSERVATIONS ON THE FUNCTIONING OF THE ALIMENTARY SYSTEM OF THE SNAIL LYMNAEA STAGNALIS APPRESSA SAY MELBOURNE ROMAINE CARRIKER Zoological Laboratory of the University of Wisconsin, Madison INTRODUCTION Although records exist of functional studies on the alimentary system of Basom-matophora as far back as the early eighteen hundreds, the detailed story of the course and ultimate fate of food in the alimentary tract and the simultaneous move-ments of the tract is thinly scattered and far from complete. In the more recent emphasis placed on some gastropods because of their importance as vectors of para-sites of man, domestic animals, wild game, and fish, it is vitally important that the normal physiology of the system most frequented by these parasites be better known. It is the purpose of this paper to integrate the previous work on the physiology of the alimentary system of Lymnaea st agnails and allied forms (suborder Basom-matophora, order Pulmonata) with original research on the same system in L. s. apprcssa Say. The basic morphological (Carriker, 1945) and histological (Car-riker and Bilstad, 1946) studies on this system in L. s. apprcssa have been com-pleted and are in press. All terms used in this research have been described in these two papers. L. s. apprcssa has been selected for this research because it is a representative vector and because of its excellent response to laboratory culture, its relatively large size (maximum shell length, 62.5 mm.) as compared with other fresh water pulmonates, its short life cycle, and its relatively thin semitransparent shell and semi-transparent tissues. Snails used in the research were cultured entirely in the labo-ratory. They were grown through many generations in large battery jars and fed on lettuce and cooked "cream of wheat" cereal. The water in the jars was aerated by means of a small Marco air pump (Noland and Carriker, 1946). The original snails were collected in Fox Lake, Wisconsin, in 1939. Parasite-free cultures (especially of trematodes) from the original snails were obtained by the isolation of the egg mass soon after oviposition in separate aquaria. Each new culture was started in this way rendering transmission of infection very improbable. Detailed examination of succeeding generations has not disclosed parasites. This work was carried out at the University of Wisconsin (1939-1943) under the stimulating guidance of Prof. L. E. Noland, whose advice, encouragement, and friendly cooperation were much appreciated. HISTORICAL REVIEW Scanty observations on the function of the anterior part of the alimentary tract of Lymnaea were given by Semper (1857), Geddes (1879) and Moquin-Tandon (1885) ; more detailed information was given by Amaudrut (1898), Pieron (1908) 88
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