194 HALF AN HOUR WITH SHELL-FISH. 



taken into consideration with their possession of an 

 embryonic shell, and certainly points in the direction 

 of their having been evolved from simpler shell- 

 bearing ancestors. 



A common example of this group is the " Sea- 

 hare " (Aplysia), so called on account of the tentacles 

 and head resembling the head and ears of a couching 

 hare. The animal is about three inches in length, 

 and is generally of a dark olive colour, varying in 

 tints and shades of other colours. It is remarkable 

 for the power it possesses of exuding a bright purple 

 fluid when dropped into the fresh sea-water of the 

 bell-glass, causing the whole to assume the appear- 

 ance of .port wine. It was formerly supposed that 

 this fluid would take off the hair, a notion which 

 gave the name of depilans to a common species. 

 The " Sea-hare " is noted for its peculiar gastric 

 arrangements, consisting of three stomachs, like 

 those of a ruminant, the middle one of which acts 

 as a gizzard, and is armed with horny plates for 

 grinding down the coarser sea-weeds on which it 

 feeds. Nearly allied to the " Sea-hare " is the " Sea- 

 lemon " (Doris), which abounds generally on the 

 perpendicular faces of rocks, and averages two or 

 three inches in length. Its popular name is derived 

 from its appearance, resembling the half of a cut 

 emon a likeness borne out by the yellow colour 

 and the warty surface. The gills, or branchiae, are 

 feathery, and eight in number, the whole being 

 expanded when the animal is in the water, like the 



