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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 conditions 

 are somewhat different, however, and the walls of the vesicles 

 are not so distinctly separated from the cerebral ganglia 

 (see Text-figs. 2 and 3). 



In the adult the infra-cerebral vesicle is covered by the 

 neurilemma or sheath of the supra-oesophageal ganglion, and 



Text-fig. 3, 



Infra-cerebral organ from young Peripatoides 

 occidentalis. x 400. 



this layer almost cuts it off from the latter. According to 

 Saint-Remy (14) and Duboscq (6) the sheath is pierced by 

 numerous pores, through which bipolar cells are to be seen 

 migrating into the brain. This is hardly the case in the adult 

 Peripatoides, as the figure shows. There are only a few fibres 

 passing from the vesicle into the supra-oesophageal ganglion 

 and but a few nuclei occur here and there. 



The cells of the vesicle itself are not of the same depth 

 throughout. Ventrally the walls are thin whilst laterally they 

 are thick, and the cells are slender, so that the nuclei lie at 

 different levels. The nuclei resemble closely those of the 

 ganglion cells of the brain mass. 



