142 LECTURE X. 



with their arms or tentacula, and to absorb by 

 means of their mouth or central orifice. They are 

 probably viviparous animals; they are in general 

 called by the popular title of sea-blubbers, and 

 are sometimes so very numerous as to float by 

 thousands on the surface of particular parts of the 

 sea. 



Another very singular genus is that of Holo- 

 tkuria, of which the characters are, an oblong, 

 nayant or floating body, furnished at one extre. 

 mity with several arms, feelers, or tentacula, sur- 

 rounding the mouth or opening. I shall here ob- 

 serve, once for all, that many of the Linnaean ge- 

 nera of the Mollusca are capable of considerable 

 improvement, and that he has somewhat too fre- 

 quently associated under one genus, animals not 

 sufficiently resembling each other in habit or ge- 

 neral appearance. The most common perhaps of 

 the European species of the present genus is the 

 Holothuria tremula ; an animal of a lengthened, 

 cylindric form, of a purplish-red colour, land beset 

 on all sides with very numerous soft tubercles of 

 different sizes; and furnished at its upper end, 

 round the mouth, with numerous short but cu- 



