26 ECHINODERMATA. 



From these I am induced to believe that the structure of this extra- 

 ordinary creature, which seems to have no parallel, will probably be bet- 

 ter understood than hitherto, for all anatomists have expressed how 

 much it has perplexed them ; and it is evident, indeed, how very slow 

 the progress of the history of the Holothuria has been, from the works 

 of Bohadsch, Muller, Tiedemann, DeUe Chiaie, and others. 



The skilful will avail themselves much more by simple inspection of 

 the engravings which have been executed after very fine drawings, than 

 of any description that I could give them. 



The Holothuria pentades is a powerful animal, capable of great 

 dilatation, and strong contraction. On laying open a large specimen, 

 and removing the intestinal organs, Mr Goadby exposed five longitudi- 

 nal muscular bands, connected by several strong tendons, which might 

 explain its strength : Plate III., representing a preparation, here reduced 

 by about a third under the natural size. 



Some of the Holothurioe die with the tentacula mthdrawn, and the 

 whole body closely contracted. But the Holothurife of this species 

 generally die with the arborescence exposed, though not expanded. A 

 general view of the internal parts is obtained from Plate IV., where the 

 orifice of the mouth a is found in the centre of the tentacula ; and on 

 one side is seen a capacious transparent vessel b, the Ampulla Poliana, 

 as named by Delle Chiaie, to which some have assigned the functions of 

 a heart. The alimentary canal is disposed in various convolutions c, d, 

 and the long ropes of a great ovarium are stretching do'vvn e. 



On divesting the body eutirely of its integument, the commence- 

 ment of the oesophagus appears, leading to the intestinal canal : Plate V., 

 a, b, c. Also the general mass of intestines below, together with the deUcate 

 reticulated mesentery, the respiratory organs d, d, and the great cloaca e. 



By a singular arrangement, not altogether unexampled, respiration 

 belongs chiefly to the organisation connected with the lower part of the 

 body of this species of the Holothuria. 



A large yellow ovoidal sac or cloaca is situated near the posterior 

 extremity of the animal, from which a continual jet is discharged by the 

 terminal orifice. This peculiar organ is secured by numerous ligaments 



