OCR Text |
Show 1892.] FROM ALGERIA AND TUNISIA. 33 The epithelial lining of the oesophagus is folded; this folding is perhaps more marked in segments xi., xii., and xiii. In segment xv. the oesophagus forms a globular dilatation, the walls of which are perfectly smooth without any folding; a very narrow aperture puts this into communication with the intestine which commences in the xvith segment. In the terminal dilatation of the oesophagus, the epithelium Fig. 1. Anterior segments of Microscolex poidtoni from the ventral surface. The segments are numbered consecutively, those of the clitellum in R o m an numerals, the others in Arabic numerals. O n the anterior thirteen segments the nephridiopores are shown in front of the dorsal seta;. The oviducal pores are on segment xiv., the male pores on segment xvii. gradually gets higher until its cells are identical in appearance with the tall narrow columnar cells which form the lining membrane of the intestine. Just at the opening of the oesophagus into the intestine, the cilia are very long and conspicuous ; but the oesophageal epithelium is also ciliated throughout the xvth segment; in front of P R O C . Z O O L . S o c - 1 8 9 2 , No. III. 3 |