OSTREA. 41 



bygone epochs, they were not so well off as we are for 

 the quality of this gastronomic luxury. Oysters seem 

 to have been as much sought for and enjoyed in the 

 " stone" age as they are at present, judging from the 

 vast heaps of large empty shells which are found in the 

 Danish kjokkenmoddings, as well as in the northern 

 parts of the British isles. 



Lister was the first to describe the anatomy of the 

 oyster, from particulars which were communicated to 

 him by Dr. Willis. This description is tolerably accu- 

 rate; and if the authority could be wholly relied on, 

 these mollusks ought not to suffer the discredit of being 

 so stupid as is proverbially alleged in Norway and 

 Brittany. Willis states that when the tide comes in 

 they lie with their hollow shells downwards, and when 

 it goes out they turn on the other side ; and he adds 

 that they do not remove from their places, unless in 

 cold weather to cover themselves with the ooze ! Lister 

 appears to have trusted too much to his friend, and not 

 to have learnt for himself the fact that oysters have 

 not the slightest power of locomotion, except in their 

 embryonic state. Bishop Sprat's account of our oyster- 

 fisheries, which has been so often quoted in works on 

 natural history, was chiefly compiled from this com- 

 munication of Dr. Willis. The " spat/' said to be like 

 a drop of candle-grease, is a pure fiction. From April 

 to July the ova are continually excluded from the ovary 

 and discharged into the gills, where they are hatched. 

 Every batch of fry in succession is then committed to 

 the sea ; and the young commence life as free animals, 

 like other bivalves, swimming or rather flitting about 

 with considerable rapidity by means of numerous cilia 

 which fringe their circumference. Each is enclosed in 

 an extremely thin and prismatic semiglobular bivalve 



