BO LOT HU BI A. 47 



what enlarged in trumpet shape ; and that the intermediate portion in a 

 inuricate or tuberculate cylinder. Possibly subordinate organization 

 might be discovered in the flattened disc ; but the opportunities of bring- 

 ing any part of the organ whatever under the microscope are so rare, as 

 to prove a great ol>-taele to inspection. \\ "ere there any question of 

 tht-ir solidity, they might l>e supposed absorbents, fojr the peculiar or- 

 ganization employed in this function is not obvious, it goes on however 

 to a great \ ^urn-times the flattened disc seemed reddish during 



observation, and conjectures were entertained of the motion of globule.- 

 or a fluid in the cylindrical part. But the illusions concomitant on arti- 

 ficial aid are MI ready to disturb the truth, that the naturalist distrusting 

 himself cannot repeat his observations too carefully, or too often, before 

 arriving at definite conclusions. The microscope demands many pre- 

 cautions. Besides the numerous suckers anchoring the subject to the 

 ides of its vessel, many free and disengaged stretch around in various 

 directions, as if in search of other objects. Several days frequently 

 elapse before weaker specimens affix themselves, therefore some exertion 

 >eems re.nii.Mte. 



The animal being secured by adhesion of the suckers, it- ]x>sition it 

 seldom changed afterwards. Curvature of the crescent may augment or 

 diminish while adhering ; and adhesion ceasing, progression may ensue. 

 For a long time I was much perplexed as to the mode wherein this wan 

 accomplished. I could not form an opinion regarding the advance of 

 the one or the other extremity. From certain indications, and especially 

 from the inadequacy of the arborescent apparatus to encounter resist- 

 ance, I rather concluded that it must be the opposite extremity ; and 

 this fact was apparently corroborated by the timidity of the animal, and 

 ite singular care to protect the tentacula. But I was mistaken : the 

 Holothuria, as most natural to believe, advances head foremost, and 

 with the arborescence displayed. Commencing progression, the sucker* 

 in front are relaxed, while those free behind are brought forward and 

 secured ; the former fix again, and the latter being loosened, the body is 

 advanced. Thus ore steps effected, and the transition of the Holothuria 



