Quarterly journal of microscopical science . ith Henkings first(larger) pair. They run as far back as do the second pairof P. ulvae and sometimes cross over in a similarfashion. The lateral diverticula of the pharynx disappear posteriorly,and the oesophagus develops a fresh series of diverticula in theform of deep longitudinal furrows. Behind the cerebral com-missure the oesophagus in most cases shows a tripartite arraiment as in By t hinella. It is ciliated almost up to its distalextremity. The stomach (Text-fig. 3) is an irregularly-shaped organ with a forked appearance exteriorly due to the
Quarterly journal of microscopical science . ith Henkings first(larger) pair. They run as far back as do the second pairof P. ulvae and sometimes cross over in a similarfashion. The lateral diverticula of the pharynx disappear posteriorly,and the oesophagus develops a fresh series of diverticula in theform of deep longitudinal furrows. Behind the cerebral com-missure the oesophagus in most cases shows a tripartite arraiment as in By t hinella. It is ciliated almost up to its distalextremity. The stomach (Text-fig. 3) is an irregularly-shaped organ with a forked appearance exteriorly due to thefact that the intestine and style-sac leave the Btomach parallelto each other from its anterior end. The oesophagus and lf,4 GUY C. ROBSON hepatic duct open into the stomach at its upper (posterior)end. The pyloric part of the intestine and the style sac arein open communication with each other, as in P. jenkinsi(Eobson, 16), by means of a longitudinal slit for a considerableway. Bregenzer does not refer to this as occurring in Text-fig. Diagrammatic reconstruction of stomach to show relationship ofcrystalline style sac. p, pylorus ; ?, intestine ; st, style sac ;I, hepatic duct : o, oesophagus. Bythinella. No mention is made by Seibold of a stylesac in Vitrella, and, as his account is painstaking amithoroughly* have to assume that the sac is absent. This isa very curious fact and one to which we shall return later. Theoesophagus and hepatic duct open into the stomach fairlyclosely together. In this region the stomach epithelium isciliated, the ciliated area being continued downwards and ANATOMY OF PALUDESTRIXA 165 forwards into the pylorus. On the side of the stomach oppositeto the oesophageal and hepatic apertures the epitheliumgives rise to a dense cuticle which occupies the major part ofthe posterior part of the stomach but diminishes anteriorly. Vitrella and Bythinella apparently differ conspicu-ously in the lining of the stomach. In the latter form onlya small part of
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