ON A NEW SPECIES OF PHTMOSOMA. 169 



and are directly continuous with the ciliated grooves on the 

 wall of the oesophagus (fig. 8). A nerve runs along the base of 

 the groove^ and on each side of the nerve is a blood-vessel ; the 

 third blood-vessel occupies the angle opposite the side bearing 

 the groove : all these three vessels anastomose occasionallyj and 

 communicate below with a large blood-sinus at their base. 



In the diagram the plane of the tentacular crown is too flat ; 

 instead of being at right angles to the long axis of the body it 

 should be raised up, and in a manner overhanging the mouth : 

 in other respects the figure represents the disposition of the 

 partSj although rather diagrammatically. 



The sides of the tentacles which are directed away from the 

 mouth are deeply pigmented, and the pigment is continued 

 into a hollow at their base (figs. 5 and 8). This hollow lies 

 partly between the two horseshoes of the tentacles, and is 

 therefore itself horseshoe-shaped ; at its dorsal end the depres- 

 sion becomes deeper, and lodges the brain. 



The most important difference between the tentacles of Ph. 

 Weldonii and Ph. varians lies in the absence of the rows of 

 those skeletal cells which formed so interesting a feature of 

 the latter species. Their place is occupied by a well-developed 

 fibrous connective tissue, which passes down into the base of the 

 lophophore, and is then continuous with the connective tissue 

 which surrounds the oesophagus, and which serves as a point 

 of attachment to the retractor muscles. The lower lip is also 

 devoid of any skeletal structures ; it is, however, very vascular ; 

 its inner surface is ciliated, the cilia being continued down the 

 oesophagus ; its outer surface is pigmented. 



The area between the lower lip and the collar, as well as 

 the inner surface of the latter, is also pigmented, although it 

 has not been possible to represent this in the diagram. This 

 continuous lining of pigment ceases at the edge of the collar ; 

 its outer surface is not pigmented. The collar is represented 

 in fig. 5 completely expanded, and covering in the head ; it is 

 usually found in this condition when the introvert is retracted. 

 It would be interesting to know whether it is ever expanded 

 in this way when the head is extended during life. I have 



