REPORT ON THE HOLOTHURIOIDEA. 115 



On examining the tentacles in Elasipoda one finds that they are always arranged in 

 a single crown. I must say, however, that I feel somewhat uncertain concerning the 

 tentacles in the genus Deima, because I never saw them fully extended (PL XLIII. fig. 3). 

 When drawn inside the body and closely crowded they appear to be irregularly disposed, 

 and have almost the aspect of a double crown. The tentacles of the Elasipoda are 

 generally to be regarded as equal in size, though it may be noted that sometimes one 

 or several present a distinct tendency to become smaller than the rest. A great number 

 of individuals of the same species having very often been at my disposal, I have had the 

 opportunity of observing that wkde the tentacles in the more adult individuals are of 

 equal size, those in the young forms are often unequal, one or more being sometimes 

 almost rudimentary ; in Oneirophanta especially this is obvious, while at the same time 

 it becomes evident that no given tentacle is smaller than the other. However, it must not 

 be overlooked, that even in fully- developed individuals of the above cited genus as well 

 as of llyodcemon, Orphnurgus, &c, some of the tentacles are more or less incompletely 

 developed, only existing in the shape of small protuberances. 



The tentacles of the Elasipoda, from ten to about twenty in number, vary considerably 

 in shape ; they resemble most the peltate or digitate type as found in the Aspidochirotas 

 and in some of the Synaptidae. A more or less stiff stem supports the terminal part, 

 which is either large, round, more or less discoidal, and without any visible processes, or 

 with rudimentary ones as is the case in Lcetmogone, llyodcemon, Achlyonice, or which is 

 comparatively small and provided with many or few, larger or smaller, simple, 

 digitiform or branched processes (comp. PI. XLIV.). Deima bears comparatively minute 

 tentacles, which seem capable of being fully retracted ; in most of the other forms which 

 belong to the order in question, only the processes or their tops are retractile. The 

 tentacular suckers, which according to Quatrefages 1 and Semper are found in a few 

 Synaptidse, are altogether lacking in the Elasipoda. 



The Holothurioidea possess besides tentacles two kinds of external ambulacral 

 appendages, which according to Semper are termed " ambulacral pedicels " and 

 "ambulacral papillae." These two kinds of appendages are either found in the same 

 animal as, for instance, in Colochirus, Troschel, Miilleria, Jager, Stichopus, Brandt, and 

 in numerous species of the genus Holothuria, L., &c, or they exist singly in different 

 species, consequently there are either only pedicels present as in the most species of 

 Cucumaria, Blainville, Thyone, Oken, Thyonidium, Diib. and Koren, Holothuria 

 vagabunda, Sel., &c, or only ambulacral papdlae as in Holothuria albiventer, Senip., 

 Holothuria squamifera, Semp., &c. The ambulacral pedicels are cyhndrical, usually of 

 a comparatively inconsiderable size, and terminate in a kind of disk-like sucker, which 

 is strengthened by a calcareous plate or plates ; the ambulacral papillae, on the contrary, 

 are conical and without any terminal disk-like sucker, are usually dorsal in position, and 



1 Meruoire sur la Synapte tie Duvemoy (Amiales des scienc. nat, 2 ser. torn, xvii., 1842). 



