184 



MIGRATION OF EGGS. 



Migration of Eggs. 



nest, wherein the young are covered for a time after 

 their birth, and this buoyant substance floats as readily 

 as sea-weed ; in other instances the eggs adhere to 

 various substances. In rivers and lakes aquatic uni- 

 valves usually attach their eggs to leaves or sticks, which 

 have fallen into the water, 

 and which are liable to be 

 swept away during floods from 

 tributaries to the main streams^ 

 and from thence to all parts 

 of the same basins. In this 

 way particular species may 

 migrate during one season 

 from the head waters of the Mississippi, or any other 

 great river, to countries bordering the sea, at the dis- 

 tance of many thousand miles. The habit of some 

 mollusks to adhere to floating wood^ appears by their 

 fixing themselves to the bottoms of ships. Some pre- 

 viously known in the Danube and Wolga, have thus 

 been brought to the commercial docks in the Thames, 

 where this species has found a home. 



We trust that this interesting portion of the works of 

 God will receive far more attention than has yet been 

 given it; and we shall rejoice, if the contents of this 

 volume are the means of stimulating many of the young 



