142 LILIAN SHELDON. 



portion of the test which grows into it. This cellulose lining 

 acquires a covering of thin epithelium, and forms a circle of 

 short, blunt, unbranched tentacles. Further down, the cavity- 

 is lined by high ciliated columnar cells, which are thrown up 

 into papillae. At the junction of the buccal cavity with the 

 pharynx there is a circle of cirri, which are unbranched, and 

 in transverse action are four-lobed (fig. 10), one lobe being 

 much larger than the other three. Two of the small lobes 

 bear tufts of cilia. 



Outside the epithelial lining of the buccal cavity there is a 

 layer of connective tissue, and around this a thick layer of 

 longitudinal and circular fibres. 



The ciliated pit is simple, having the conditions found in 

 Ascidia and Ciona. Its opening into the mouth is crescent- 

 shaped, and it passes back thence, as a simple tube lined by 

 high columnar ciliated cells, below the ganglion, at about the 

 middle of which it opens out into the hypophysial gland, 

 which lies immediately ventral to the ganglion. It has no 

 communication with the latter. 



The Pharynx. — The endostyle starts from the point where 

 the buccal cavity joins the pharynx, and passes round its 

 posterior end, ceasing where the oesophagus passes off (fig. 4, 

 End.). It is very similar to the endostyle of other Ascidians, 

 bearing a tuft of very long cilia at its base and shorter ones at 

 the sides of the groove (fig. 9, c.c). Between the masses of 

 cells, which bear the cilia, are situated groups of much higher 

 cells (fig. 9), while on each side, between the most external 

 masses of ciliated cells and the ciliated epithelium of the 

 pharynx, there is a row of cells which appear to secrete mucous 

 (fig. 9, m. c), as they appear when seen in transverse section 

 to be throwing out irregular processes towards the cavity. At 

 the anterior and posterior end of the endostyle its open edges 

 are fused, so as to form a tube (fig. 8). This is an interesting 

 point, as tending to confirm the theory of its homology with 

 the thyroid body of the higher Vertebrata. 



A thin lamina (the "dorsal lamina "), covered by low 

 columnar ciliated cells (fig. 5, D. L.), projects from the median 



