ECHINODERMATA. 



199 



secure abode. Reaumur has minutely examined 

 the arrangements of their muscular fibres, and 

 has described the actions by which they either 

 attach themselves to the surfaces of rocks, or 

 effect their sluggish movements.* 



6. Echmodennata . 



ASCENDING in the scale of organization we come 

 to the Echmodennata, a class which compre- 

 hends the families of the Asterida, the Echinida, 

 the Holothurida, and the Crinoidea, together 

 with other tribes of less note. 



89 



88 



These animals, both in their general form, and 

 in the arrangement of their internal organs, 



* Memoires de I'Academie des Sciences, 1710, p. 490. 



