Sensory of reactions Holothuria surinamensis. 249 



July 19. 8,30 A.M. Regeneration cones 4 — 6 mm long on the 

 new anterior ends ; most of the time they were kept well invaginated. 

 The cones were of much less diameter than the rest of the body. In 

 two cases 11 tiny new tentacles were counted, together with several 

 papilliform growths, evidently representing the fundaments of other tentacles ; 

 in another specimen 9 well formed tentacles, 1 very small one, and 8 

 stumps were counted. The new tentacles were thin and pale , and 

 approximately 2 mm long. 



July 22. Extreme length of regenerated pieces, 1,0 — 1,3 cms. 



Exp. 72,1. Posterior end removed. 



July 14. Posterior ends, 5 mm long, removed from 5 animals. 

 The new posterior ends rolled in almost immediately (5 min.) ; the 

 amputated pieces closed the wounded end in 10 min. 



July 15. A distinct opening at the new posterior ends. 



July 17. Small regeneration cones visible. 



July 20. The new integument thin and bulging, regeneration cones 

 3 — 4 mm long. 



July 22. All dead, through accidental stagnation of the water. 



Experiments in which cuts were made with purposely ragged outline, 

 and in which pieces were removed by slanting cuts, gave results not 

 essentially different from those already described. Wound closure was 

 more successful when the cuts had smooth edges, as otherwise the ragged 

 parts were sloughed off; slanting cuts were closed in exactly the same 

 manner as those made perpendicular to the long axis of the body, but 

 the thinner part of the cut end was also sloughed off in most instances. 



Some tests were made with animals kept in M/800 chloretone^ 

 in the hope of eliminating by this means the action of the muscles 

 in bringing about the inrolling of the wound edges. It was found 

 that with chloretoned animals the rapid in-bending did not occur^ 

 though after an hour or more the edges of transverse cuts were 

 slightly curved. It would therefore seem that the direct action of 

 the injured muscles plays a more prominent part in wound closure 

 ill Holothuria than it does in actinians (Rand, 1909; Chestee, 1912). 



Holothuria surinamensis can therefore regenerate, or rather re- 

 form from its body-tissue (for the operated animals were kept in 

 aquaria without sand or mud to provide nutritive material) an 

 anterior or a posterior end within a very brief interval after the 

 removal of those parts. The significance of this power, as favorable 

 to a method of reproduction by self division, has already been 

 pointed out (page 243). The incomplete restoration of the usual com- 

 plement of tentacles would account, in part at least, for the nume- 

 rical variation of these structures found in some specimens. 



17* 



