BULLETIN OF THE UNITED STATES FISH COMMISSION. 293 



Professor Motrins has published an account of his discovery in No. 

 134 of the Zoologiseher Auzeiger, of the 19th of March, 1883. 



The discovery of this parasite and its subsequent study was made in 

 precisely the same way as by the writer. The contents of the stomach 

 of the oyster were removed by thrusting a pipette or medicine-dropper 

 into the mouth of the animal, and drawing out by that means the juices 

 and the microscopic food which the stomach contained. Almost every 

 other oyster examined, and sometimes every one, will be found to be in- 

 habited by this creature ; but no ill effects, so far as the writer is aware, 

 are traceable to its presence when infested oysters are consumed by man 

 as food. It seems to be a perfectly harmless commensal or pensioner 

 upon the oyster whose stomach it inhabits. 



THE FOOD OF THE OYSTER. 



The method of removing the contents of the stomach of the oyster 

 with a pipette is valuable for another very important purpose, namely, 

 to learn the nature of the food which the animal had taken shortly be- 

 fore. This season, while examining oysters in Chincoteague Bay, with 

 this object in view, I found that the adults were guilty of swallowing 

 sometimes as many as 200 of their own young at one meal. These young 

 oysters ranged in size from one five-hundredth to one two-hundredth of 

 an inch in diameter, and already had the shell developed; and the 

 larger ones were found to be themselves feeding, inasmuch as food could 

 be seen in their stomachs. 



Besides these young oysters a good many oyster eggs were also found 

 amongst the contents of the stomach, together with spermatozoa, dia- 

 toms, the very youngest stages of barnacles, and the shells or external 

 coverings of a singular infusorian, which was identified as a species of 

 lintinnus. Of this last organism, several thousands of tbeir shells were 

 sometimes met with in the contents of the stomach of a single oyster. 



The fact that adult oysters swallow their own young and eggs shows 

 that they may be, in this way, to some extent, destructive of their own 

 species. 



The investigation of the contents of the stomach and intestines of the 

 oyster by the method already described on an extensive scale in differ- 

 ent localities along the eastern coast of the United States is important; 

 because it is a well-known fact that the flavor of oysters varies or is af- 

 fected by local causes which are probably mainly the food and the saline 

 condition of the water in which they grow. 



The contents of the stomachs of a great number of individuals could 

 be very readily removed and preserved for investigation by the means 

 which the writer has used. The identification of the minute vegetable 

 and animal remains in such material preserved for study could readily 

 be carried on by specialists versed in the characters presented by the 

 various forms. 



Possibly the most important of the food elements of the oyster are 

 diatoms. These free-swimming, minute plants are found in vast num- 



