LECTURE X. 
123 
The marine Genus Aplysia, is nearly allied to 
that of Limax, but of a somewhat more compli- 
cated structure. 
The genus Doris, which is also marine, is 
greatly allied to that of Limax, and the species, 
which are numerous, are often called by the name 
of sea-snaUs, Among these one of the most com- 
mon is the Doris papulosa of Linnaeus j of the size 
and colour of the brown slug, but covered or 
bristled over with numerous, soft, pointed processes^. 
The Linnaean species of the genus Doris differ so 
considerably in habit or general appearance in the 
different tribes, that Monsr. Cuvier and others 
have instituted for them several distinct genera, 
instead of grouping them all together, as Linnaeus 
has done. Among the most beautiful is the Doris 
radial a of the Gmelinian edition of the Sy sterna 
Naturae. It is found in the Atlantic ocean, and 
is about an inch in length, of a very fine deep- 
blue colour, accompanied by a silvery lustre, and 
is distinguished, as a species, by having on each 
side the body three pair of spreading tufts or pro- 
cesses, of a blue colour, and each consisting of se- 
veral distinct, diverging rays or fibres. 1 have be- 
fore observed that it is not my intention to pass with 
