N UDIBRANCHS — DORIS. 



37 



for the elegant form and brilliant colouring of 

 their habitations, they seem to be equalled^ if not 

 eclipsed, in beauty by a race of molluscs which 

 possess no shell at all, and whose chief beauty is 

 derived from the singular peculiarity of forma- 

 tion from which their name is derived. These 

 are the Nudibranchs, or Naked-gilled Molluscs, 

 so named because their respiratory apparatus, 

 instead of being concealed within their bodies, 

 or defended by shells, is placed upon the ex- 

 terior, in apparently heedless defiance of sur- 

 rounding objects. And the more that the delicate 

 construction of these branchiae is seen, the more 

 wonderful does it appear that these organs should 

 be placed in the position which they occupy 

 without suffering serious injury. If the lungs 

 of one of the mammalia were to be attached to 

 its sides, and permitted to hang loosely there- 

 from, exposed to the invasions and collisions to 

 which they would probably be liable, the owner 

 of the said lungs would hardly feel comfortable. 

 But the lungs, gills, or branchiae, of the mollusc 

 are so exceedingly delicate, that the mammalian 

 lung appears quite coarse by their side. 



There are many species of Nudibranchs found 

 on our coasts, one of the commonest of which 

 {Doris ptilosa) is represented on plate n, fig. 4. 



