434 G. H. PARKER AND E. G. TITUS 



form diameter, after which it expands as the oral disc is ap- 

 proached. It is ribbed longitudinally by the insertion lines of 

 the numerous mesenteries. At about one fifth its length from 

 the oral end, it is marked by a well defined circular collar indi- 

 cating the position of the sphincter muscle. On the oral side 

 of this collar the column wall is translucent and thin and the 

 attachment of the mesenteries can be easily seen through it. 

 On the pedal side of the collar, the column wall is much more 

 dense and thick and the attachment of the mesenteries is in- 

 dicated only by faint longitudinal ribs. This portion, more- 

 over, is characteristically colored, brown, orange, whitish, or 

 some mottled combination of these. This area when closely 

 examined will be seen to present a considerable number of minute 

 pores, the cinclides, by which the central cavity of the sea- 

 anemone may communicate with the exterior. The finer struc- 

 ture of these openings has been well described by Carlgren 

 ('93, p. 103). 



The oral disc contains near its center the mouth, a more or 

 less elongated opening surrounded by the protruding lips. The 

 lip§ are coarsely grooved, the grooves extending downward into 

 the oesophagus. Specialized hp grooves, the siphonoglyphs, 

 are almost always present, commonly one, often two, and 

 rarely three, a condition also found in M. dianthus by Carlgren 

 ('93, p. 104). Surrounding the lips is a narrow intermediate 

 zone carrying no speciahzed structures and connecting with 

 the peripheral or tentacular zone. This is broadly lobed on 

 the edge, where it passes over into the wall of the column; it 

 carries a multitude of tentacles. The tentacles are largest 

 near the mouth and become successively smaller as the periphery 

 of the disc is approached. Their number is enormous and cer 

 tainly amounts to thousands in a large individual. 



We have been unable to confirm Carlgren's statement ('93, 

 p. 104) that the tentacles of Metridium have terminal pores. 

 We could not identify these pores in sections nor by forcing 

 fluid through them. If a Metridium is anaesthetized in a solu- 

 tion of magnesium sulphate in sea-water, it is then easy to in- 

 ject into its gastro vascular cavity dissolved methylene blue. 



