ON TURBELLARIA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 827 



EXPLANATION OF FIGURES. 



ag. Anterior gut root or its branches. mu. 



hr. Brain. mu.s. 



br.e. Eyes belonging to the brain area group. p. 



ep. Surface epithelium. pe. 



fa. Female aperture. ph. 



fo. Female organs (undeveloped) in fig. 3. p.ho. 



g. Main gut. ph.s. 



g.l. First lateral gut root. ps. 



g.2. Second ,, ,, s. 



g.3. Third „ „ sg. 



gr.g. Granule gland (prostatic vesicle). I. 



m. Mouth. vs. 



ma. Male aperture. ut.d. 



mc. Mucous canals in the muscular tissue behind id. 



pharyngeal sac. 



Muscular layer of body wall. 



Sphincter muscle of pore canal in fig 3. 



Dorsal pore. 



Penis. 



Pharynx. 



Internal opening of pharynx. 



Pharyngeal sac. 



Penis sheath. 



Sucker. 



Shell gland. 



Tentacle. 



Vesicula seminalis. 



Efferent canal of uterus. 



Commencement of uterus. 



DESCRIPTION OF PLATE— (For lettering see above.) 



Fig 1. Sagittal section of Aceros stylostomoides (specimen a). 



Fig. 2. Dorsal pore of A. stylostomoides (specimen b). The canal is oblique and of considerable length, 

 its lumen being fairly uniform but slightly contracted near its inner and outer ends. The cells lining it are 

 richly ciliated. 



Fig. 3. Sagittal section through genital region of immature Nuchenceros orcadensis, highly magnified. 

 Description on p. 7. There is no connection at this stage between the various cavities and the external 

 surface. 



Fig. 4. Sagittal section of Nuchenceros orcadensis (specimen b). 



Fig. 5. Sagittal section of N. orcadensis (specimen a). 



Fig. 6. Longitudinal section of N. orcadensis (specimen a), passing through the tentacle on one side. 

 The absence of visceral branches in the substance of the tentacle will be noted. 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART III. (NO. 29). 



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