1885.] NEW-YORK MICROSCOPICAL SOCIETY. 61 



mollusk is eaten when taken on the half-shell. This large spot 

 which I make is the adductor muscle, with which the creature 

 pulls together its shells. It is the part which is cut through with 

 the knife when the caterer opens the bivalve. Well to the left 

 of this I draw four plates, or leaves, so lying on one another as 

 to show their outer edges, which give the appearance of a frill. 

 This series of plates constitutes the gills, or breathing apparatus. 

 Now, here we find the inner edges of these four plates to be, 

 so to speak, soldered together, making the base of the gills ; 

 and along this base, in rows, is a series of holes. The plates are 

 really composed of an infinite series of microscopic tubes, each 

 tube being like a tiny flute with holes on the side. The water 

 enters between the plates, and as the surface of the tiny tubes 

 is covered with cilia, or fleshy hairs, these keep up a lashing by 

 which the water is driven through the gill-tubes, and the air 

 contained in the water is deprived of its oxygen ; after which 

 the disaerated fluid passes out at the holes in the bases of the 

 gills. The coarse cilia, or beard, on the edges of the mantle, or 

 thin film which enwraps the oyster, by their action make an 

 eddy at the opened valves, into which the water rushes, bring- 

 ing in the food. The outer surface of the gills is covered with 

 the minute cilia, all helping to drive the inflowing current up- 

 ward. Here at the uppermost end of the oyster, near the hinge, 

 are four little plates, not lying upon one another, as the gill- 

 plates do, but standing together, as it were. These are the 

 labia, or lips of the oyster ; for, in fact, the creature's mouth is 

 simply the orifice between these two pairs of lips. When the 

 food-laden water reaches this spot, the lips begin a sorting proc- 

 ess, by which that which is fit for food is allowed to enter, and 

 the unfit is rejected. The oral aperture is almost immediately 

 over the stomach, the passage being too short to be properly 

 called a. gullet, or oesophagus. Yet the word is convenient. 

 Thus the stomach receives the food immediately. The dark 

 gray mass in which this organ is imbedded, is the liver. The 

 oyster's stomach is, literally, inside of its liver. Let us now 

 note the course of the intestinal tract. Beginning at the lower 

 end of the stomach, or where in our own structure would be the 

 pylorus, the intestine runs to a point considerably beyond the 

 m'ddle of the adductor muscle, between that and the gill 

 bases. Here it doubles upon itself. Then, returning, it passes 



