78 TESTACEA. 



They thrust the foot so forcibly downwards that the whole animal is 

 elevated. 



It is very much of the nature of the Ascidia, — at least the upper 

 ])ortion. 



The shell opens by a cartilaginous hinge, running down the whole 

 back and uniting the valves. The front of the body is open from about 

 the middle, the body there consisting of a thickish tunic lining each 

 valve, and allowing the foot to descend. This foot seems to be chiefly 

 occupied by a very dilateable internal cavity. 



It seems very difficult to preserve these animals alive. 



After being kept a short time, the edges of the shell recede from 

 each other, which corresponds with the gaping of other bivalves, and this 

 recession continues augmenting, from the weakness of the animal, until 

 it perishes. It is not explained whether the creature's position in the 

 sand is horizontal or perpendicular. Probably the latter, to allow the 

 orifices to be fi'ee. 



Plate XVIII. 

 Solen siliqua. 



I shall abstain from further notes on the Testacea at present ; nor, 

 unless for the concomitant drawings of the animals, in vigorous anima- 

 tion, should so much have been said. 



THE OYSTER FISHERY. 



Perhaps the Oyster fishery merits a few observations, as of greater 

 ])ublic interest, in an economical view, and especially from affording a 

 number of people the means of earning a livelihood. 



The oyster is abundant in various parts of Scotland, " dwelling at 

 various depth of water. I have been assured that there are oyster beds 



