Sensory reactions of Holothuria surinaraensis. 235 



Biological Station during- the summer of 1913; and to thank, also, 

 Prof. W. M. Chester, in charge of the Laboratory during a part of 

 the season, in the absence of Dr. Maek, for many kindnesses. To 

 Mr. D. H. WENßiCH I am indebted for assistance during the course 

 of the work. 



II. The species studied. 



1. Anatomy. 



The species chosen for detailed study was Holothuria surinamensis 

 Ludwig (1875). It has been reported from Bermuda by Clark (1898, 

 1899, 1901b), and by Verrill (1906). Figures showing the general 

 proportions of the body are given by Clark (1901c, tab. 17, fig. 1) 

 and by Verrill (1906, p. 322, fig. 172). Semper's plate (1868, 

 tab. 28) of H. coluber Semp. gives a more nearly correct idea of the 

 appearance of the animal.^) 



Some 250 individuals were employed in the course of my 

 experiments ; smaller numbers of the related forms H. captiva Ludw., 

 H. rathbuni Lamp., Stichopus moehii Semper, and Cucumaria punctata 

 LuDw. afforded comparative data on certain points. 



Though essentially similar in structure to Tliyone and Cucumaria 

 (Dendrochirotae), the genera Holothuria and Stichopus (Aspidochirotae) 

 present certain anatomical differences which are of importance in 

 comparing the reactions of the two groups. Holothuria surinamensis 

 has a vermiform body of approximately constant diameter thruout 

 its length, but narrowing slightly at the anterior end about the 

 mouth and posteriorly about the cloacal aperture. Animals employed 

 in these experiments were usually 10 — 15 cms in length by 1,5 — 2,0 cms 

 in diameter, when normally extended. The buccal orifice lies in 

 the center of a pale smooth area, directed somewhat ventrad, 

 and surrounded by a circlet of short peltate tentacles. The number 

 of these tentacles is variable, as in H. floridana (Edwards, 1908) and 

 other forms. Clark (1899, p. 121) records 20 as the modal frequency, 

 with a range of 10 — 21. My observations are in agreement with 



1) Clark (1899, p. 121) finds that Bermuda specimens differ slightly 

 from Ludwig's original description of H. surinamensis from Surinam, in 

 minor features of the calcareous deposits of the skin and "lantern". 

 "While these differences are not considered to be of specific rank, they are 

 pointed out also in specimens from Jamaica and Porto fiico (Clark, 

 1901c, p. 359). 



