56 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



1. A very delicate supporting layer (a). 



2. An outer layer of cells (6), continuous with the 

 ectoderm cells of the outer surface of the velum. 



3. An inner layer of cells (c), continuous with the ecto- 

 derm cells of the inner surface of the velum. 



b. The otolith (d) is surrounded by a delicate layer of 

 protoplasm, by which it is attached to the inner surface of 

 the capsule. 



c. Four or five fine sensory hairs project from the wall 

 of the capsule towards the otolith. 



IX. STRUCTURE OF THE STARFISH. 



( Aster acantheon beryiinus.) 

 THE HARD PARTS. 



SPECIMENS of the common starfish may be found in 

 abundance at low tide at almost any point on our north- 

 ern coast, although on the more sandy southern coast it 

 may be necessary to dredge for them in deep water. The 

 ordinary oyster-dredge may be used, and specimens can 

 usually be obtained by dredging upon oyster-beds. Some 

 should be preserved in alcohol, and some dry. Those 

 which are to be kept in alcohol should be slit with the 

 point of a sharp knife along the upper surfaces of the 

 rays in order to allow the alcohol to penetrate them, and 

 they should then be placed in seventy-five per cent alco- 

 hol. This should be poured oft' and renewed within a week 

 or less, and replaced by fresh alcohol. 



The specimens which are to be dried should be placed, 

 alive, in a flat-bottomed dish of warm fresh water, and 

 left for ten or fifteen minutes. They should then bo laid, 

 flat, in enough seventy-five per cent alcohol to cover them, 

 and in about an hour taken out and dried in the sun, or 



