LECTURE X. 123 



The marine Genus Aplysia, is nearly allied to 

 that of Umax, 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-snails. Among these one of the most com- 

 mon is the Doris papillosa of Linnaeus ; of the size 

 and colour of the brown slug, but covered or 

 bristled over with numerous, soft, pointed processes. 

 The Linnsean 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 

 radiata of the Gmelinian edition of the Systema 

 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. I have be- 

 fore observed that it is not my intention to pass with 



