126 
LECTURE X. 
no appearance of any regular viscera or inter- 
nal organs, but the vrhole presents a continued 
vacuity. The colour of this curious animal, when 
at rest, is a pale greenish blue j but wheij in mo- 
tion, which is performed by the alternate con- 
traction and dilatation of the body, the whole 
appears in the highest degree of phosphoric lustre, 
passing through all the colours of a bar of red- 
hot iron, till at length it becomes of what is term- 
ed a white-heat ; after which it again passes into 
the colour of red-hot iron, and from that gra- 
dually declines into its original greenish hue. The 
length of this animal is that of several inches, and 
its diameter about a fourth or fifth of its length. 
It is a native of some particular parts of the At- 
lantic Ocean, where it is seen in great multitudes, 
and irradiates the waves with its fiery brilliancy. 
Linnceus would perha|:ks have been inclined to have 
made it a species of Holothuria. 
In the enlarged edition of the Sy sterna Natu- 
rae by Gmelin, some of the small fresh-water spe- 
cies of the Liniifean genus Nereis are more pro- 
perly referred to a new and distinct genus, under 
the name of JVais, As an example of this genus 
may be mentioned a very small, transparent, and’ 
