18 LIFE BY THE SEASHORE. 



a succession of remarkable changes before they attain the 

 adult form. Our present interest in these cases is due to 

 the fact that the peculiarities of the larvae ensure the dis- 

 tribution of the species, and compensate for the limitations 

 of that sedentary life which the exigencies of shore life 

 force upon so many of the adults. But we shall see later 

 that these Iarva3 are also of great interest in possibly 

 throwing light upon the origin of the animals of the sea- 

 shore, and upon their relations to the animals of the other 

 parts of the ocean. 



