6 



straining out the minute particles from the water. i\Iolluses, 

 shrimp, worms, hyclroids (''frog's hair" and small jelly fish), 

 sponges and even the adult oyster itself which may destroy 

 many thousands of its own spawn, all help to diminish the 

 number of larvae by using them as food. But in spite of all 

 these natural enemies, the actual number destroyed by them 

 probably amounts to a far less percentage than what die from 

 lack of suitable conditions to continue growth after reaching 

 the stage where they must attach themselves for further growth. 

 Of the millions that are carried out to sea, or drifted into fresh 

 water, or fall on a soft muddy bottom, not one is destined to 

 survive. At this stage, the larvae need some clean surface to 

 attach themselves to. If they do not find it, they fall to the bot- 

 tom and soon perish. The surface on which they are destined 

 to become attached, must be free from slime and other animal 

 or vegetable growth. If favorable conditions present themselves, 

 the young oyster attaches itself by one valve to some solid sup- 

 port, and remains there for the rest of its days. 



The Feeding of the Oyster. — From now on, the oyster is 

 permanently fixed, and both food and oxygen have to be gotten 

 from the water immediately surrounding it. The food of the 

 oyster consists mainly of microscopic plants, such as diatoms, 

 and floating bits of sea algae. But the oyster cannot discrimin- 

 ate and may take in or reject everything that is caught by the 

 gills. 



Prof. James L. Kellogg, of Williams College, who has made 

 a specialty of the study of the ciliary mechanisms by which 

 minute organisms, floating in the water, are collected by the gills 

 and either passed on to the mouth or thrown out, states : 



"It appears that the animal (oyster) is not able to dis- 

 tinguish food from mud particles, either by the gills or by the 

 palps (lip-like process around the mouth) but the selection 

 of food results directly from the differences in the response 

 of the palps to varying quantities of matter transported to them 

 by the gills. Under favorable conditions, diatoms are collected a 

 few at a time, and are sent across the palp ridges to the mouth. 

 In muddy water, the particles increase in number until the 



