OR, GLIMPSES BENEATH THE WATEES. 



tion of a small pickled Gherkin as can be conceiyed, 

 except in colour, the shells or cases of these ani- 

 mals being generally white. One of the species, 

 Syalina, has a case which seems formed of 

 crisp rice-paper, and is covered with spines of the 

 the same colour and texture. The tentacula, or 

 breathing apparatus, eight in number, are curiously 

 branched, and, when expanded, have the appearance 

 of a skeleton flower, of which the figure in Plate 

 IX. will convey a tolerable idea. The functions of 

 this flower-like set of organs are probably the same 

 as those of the Nudihranch class of Molluscs^ which, 

 though generally considered as being a breathing 

 apparatus, are, probably, at the same time food- 

 collecting organs, as all the creatures thus furnished 

 are liquid feeders. 



Thy one papillosa^ one species of Sea-Cucumber, 

 has ten branches to this set of organs, which it sel- 

 dom displays when in captivity; but a little gentle 

 motion artificially imparted to the water, as sug- 

 gested in another place, would probably produce the 

 kind of excitement requisite for their expansion, as 

 the introduction of fresh water to the tank seldom 

 fails to produce this effect for a time. When irritated, 

 these creatures have the capacity of committing self- 

 destruction in a most determined and complete man- 

 by 



