THE OYRTEP. AISTD THE OYSTER TT^DUSTEY. 



11 



From this cavity the water passes behind the adductor muscle and 

 out between the edges of the valves of the shell around tlie rear end 

 of the gills, at a point in the upper left of the figure. 



The food of the oyster consists entirely of minnte animal and vegetable organisms 

 and small particles of organized matter. Ordinary sea water contains an abundance 

 of this sort of food, which is drawn into the gills with the water, l)ut as the water 

 strains through the pores into the water tu^. the food particles are caught on the 

 surface of the gills by a layer of adhesive slime ,. ''"h covers all the soft parts of the 

 body. As soon as they are entangled the cilia strike ..gainst them in such a way as 

 to roll or slide them along the gills toward the mouth. When they reach the anterior 

 ends of the gills they are pushed off and fall between the lips, and these again are 

 covered with cilia, which cany the particles forward until they slide into the mouth, 

 which is always wide open and ciliated, so as to draw the food through the oesophagus 

 into the stomach. Whenever the shell is open these cilia are in action, and as long as 

 the oyster is breathing a current of food is sliding into its mouth.a 



The food then passes to the stomach, is acted on by the fluids from 

 the liver, and moves along the intestine. The nutritive portion is 



Fig. 1. — PiaKram of dissection of oyster to show reproductive organ, consisting of the branching tubules 

 spread over the dotted portion.' au, auricle of heart; d, external opening of reproductive organ; g, 

 gills; M, adductor muscle; m, mouth; p, palps; ve, ventricle of heart; y, posterior end of gills. About 

 natural size. (After Moore.) 



absorbed and the feces are thrown out the vent in long, ribbonlike 

 form and carried outside the shell with the stream of water passing 

 out from the chamber over the gills, 



Tlie position, form, and general appearance of the reproductive 

 organs of the oyster are the same for both sexes. Really there is but 

 one reproductive organ, which consists of a mass made up of micro- 

 scopic tubules and connective tissue lying between the folds of the 

 intestine and investing it and the stomach and liver in such a manner 

 as to cover the visceral organs when the opened oyster is viewed from 

 either side. In Plate II most of the reproductive organ has been 

 removed, a small portion being shown about the folds of the intestine. 

 Text figure 1 represents an oyster with the left valve and mantle 

 removed, showing the reproductive organ as it appears from the 

 left side, covering the visceral mass and partially surrounding the 

 heart and adductor muscle. Numerous ducts arise from the organ, 

 unite into one and open at point d below the adductor muscle. A view 



a Brooks, W. K. (1880. p. 9.) 



