236 W. J. Ceozier, 



this statement, and evidence was obtained (see page 249) which indicates 

 that the variation in numlber of tentacles is in part to he accounted for 

 through regeneration of the anterior end. In specimens about 10 cms 

 long the tentacles are approximately 5,5—6,0 mm in length, 0,5 mm 

 in diameter along the shaft, with peltate discs about 1,5 mm broad. 

 The tentacles have a semicircular valve situated at the base near 

 the ampulla, which when expanded allows the erected organ to be 

 moved about hj the muscles of its wall. Immediately behind this 

 circlet of modified tube-feet is a collar, the "brim", with a scalloped 

 edge, which may be so contracted as to close down over the retracted 

 tentacles and the mouth. The ventral surface of the animal is 

 slightly flattened, though not to such an extent as in H. captiva or in 

 Stichopus; on it occur the irregularly scattered pedicels, about 10 — 16 

 of them per square centimeter. The pedicels are about 2,5 mm 

 long when normally extended. On the dorsal and lateral surfaces 

 are slender tapering papillae, modified pedicels, which bear no 

 sucking-discs; they are 2 — 3 mm long, usually, and are not so 

 numerous, relatively, as the pedicels. The papillae are frequently 

 borne on blunt tubercles. Occasionally papillae with divided or 

 duplicate tips were found. The cloaca terminates in a circular 

 opening, which is rhythmically opened and closed by special muscles; 

 the pumping action of the cloaca — accomplished by muscle strands 

 running to the body- wall and by an anal sphincter, and assisted by 

 the activity of the general body musculature and the muscles of the 

 respiratory trees (Henri, 1903d) — forces water in and out of the 

 respiratory trees. Surrounding the cloacal aperture is a brim, which 

 bears a distinct ring of papillae. The color of //. surinaniensis is a 

 general brown, varying from a yellowish tint to olive and occasionally 

 to almost black; the ventral surface is much lighter than the dorsal, 

 while the tentacles, oral surface, edge of the collar, pedicels and 

 tips of the papillae, are yellow. Darker patches are sometimes present 

 on the upper surface, especially about the bases of papillae. 



Of the internal arrangements, which conform to the description 

 of conditions in other well known species of Holothiiria, attention 

 need only be called to the five radial bands of longitudinal muscles 

 and the interradial muscle strands perpendicular to them. Three of 

 the longitudinal bands constitute the ventral "trivium", the two dorsal 

 ones forming the "bivium". The walls of the podia are also contractile. 

 Special retractor muscles, such as control the extension of tentacles 

 in the Cucumariidae. are not present in Holothuria. Histologically 



