238 CUTTLE-FISH, MOLLUSC A, ETC. 



very beautiful and attractive objects. In another 

 group (Tectibranchiata) commonly to be seen in ma- 

 rine tanks is the Aplysia, or " sea-hare " so called 

 on account of the rude resemblance of the head and 

 shoulders to those of a " sitting hare." The Dons, or 



Fig. 169. 



Sea-slug (sEolis coronata). 



"sea-lemon," well deserves its popular name both 

 from its colour and general appearance. These sea- 

 slugs usually construct very pretty " nidal-ribbons," or 

 egg-cases, in which the eggs are placed in thick rows, 

 like beads closely stitched over the surface of a piece 

 of ribbon. 



Among the bivalves, we cannot wonder that the 

 oyster and the mussel are favourites. The latter is 

 abundantly kept in the tanks, on account of its enor- 

 mous powers of reproduction. The issue from a 

 single living specimen would soon multiply at such a 

 rate as to clothe the entire surface with dense masses 

 of mussels ; but the young are greedily sought after 

 by many fishes, &c., so that they are advantageously 



