Quarterly journal of microscopical science . tion through thehead. The structure is referred to below. The infra-cerebral organs appear in dissections to hang fromthe supra-oesophageal ganglion by short stalks. In seel , they appear more closely attached. The differencein appearance is due to the transparency of the suspendingmembrane which is the structureless, almost non-staining,sheath of the ganglion. In Peripatoides occidentalisthere is generally a region that one might term the peduncle,within which are a few scattered nuclei and a small numbei 412 WILLIAM J. DAKIN of delicat
Quarterly journal of microscopical science . tion through thehead. The structure is referred to below. The infra-cerebral organs appear in dissections to hang fromthe supra-oesophageal ganglion by short stalks. In seel , they appear more closely attached. The differencein appearance is due to the transparency of the suspendingmembrane which is the structureless, almost non-staining,sheath of the ganglion. In Peripatoides occidentalisthere is generally a region that one might term the peduncle,within which are a few scattered nuclei and a small numbei 412 WILLIAM J. DAKIN of delicate fibre-like strands. They might be nerve-fibres or,on the other hand, merely processes of non-nervous cells. In young and small Peripatoides (Text-fig. 3) the conditionsare somewhat different, however, and the walls of the vesiclesare not so distinctly separated from the cerebral ganglia(see Text-figs. 2 and 3). In the adult the infra-cerebral vesicle is covered by theneurilemma or sheath of the supra-oesophageal ganglion, and Text-fig. Infra-cerebral organ from young Peripatoidesoccidentalis. x 400. this layer almost cuts it off from the latter. According toSaint-Bemy (14) and Duboscq (6) the sheath is pierced bynumerous pores, through which bipolar cells are to be seenmigrating into the brain. This is hardly the case in the adultPeripatoides, as the figure shows. There are only a few fibrespassing from the vesicle into the supra-oesophageal ganglionand but a few nuclei occur here, and there. The cells of the vesicle itself are not of the same depththroughout. Ventrally the walls arc thin whilst laterally theyare thick, and the cells are slender, so that the nuclei lie aldifferent levels. The nuclei resemble closely those of theganglion cells of the brain mass. INFRA-CEREBRAL ORGANS OF PERIPATIS 413 The cavity of the vesicle is most usually empty, but some-times contents are present, and the most conspicuous exampleof this kind has been figured (Text-fig. 2). In this spec
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