STUDIES ON THE ANATOMY OF LYMNAEA HUMILIS SAY

Abstract

The topographic anatomy of Lymnaea humilis is described, giving the relative positions of the various internal organs. A description of the anatomy of the cephalic hemocoele is also given. Like Lymnaea stagnalis the central nervous system of L. humilis consists of the paired cerebral, buccal, pedal, pleural, and parietal ganglia and the unpaired abdominal ganglion. The nerves arising from the central nervous system are described and particular attention was devoted to the nerves arising from the pedal ganglia and innervating the foot; fourteen new nerves are named or described. The reproductive system of L. humilis is divided into: (a) the ovotestis and its duct, (b) the female system, and (c) the male system. In reproductively active snails, the female system is the largest of the three portions, and consists of the uterus, oothecal gland, vagina, and seminal receptacle. An accessory structure, the albumen gland, is very large in L. humilis. The male system consists of the upper and lower prostate, vas deferens, and male copulatory organ. The connections between the hermaphrodite duct and the male and female systems show considerable structural consolidation compared to these connections in L. stagnalis. The muciparous gland is not a distinct entity in L. humilis.