250 SEASIDE DIVINITY. 



quarter to six-eighths of an inch at the base, and 

 from a quarter to half an inch in height. Others 

 are considerably larger, being an inch and a half 

 in diameter at the base, and from half an inch to 

 an inch and a quarter in height. These shells on 

 superficial examination appear as if formed of 

 one piece. But this is not the case. They are, 

 as already stated, composed of several pieces, and 

 this circumstance is of the greatest importance, 

 being absolutely necessary as a provision for the 

 growth of the animal. This circumstance caused 

 them formerly to be classed with the multivalve 

 shells, and the animal was classed with shell-fish 

 or mollusca. But their structure is now better 

 understood, and the acorn-shells and barnacles 

 form a small class with characteristic peculiarities 

 of their own, although allied to the Crustacea. 



Like the various kinds of actiniae and other 

 marine animals, the inhabitants of these acorn- 

 shells are entirely inactive when no longer covered 

 with water. But as soon as the tide rises they 

 project from the opening in the upper part of 

 the shells the apparatus from which their name 

 curl-footed is derived. This has a striking resem- 

 blance to a plume of feathers, the motions of 

 which are extremely regular and graceful. This 

 apparatus is adapted at once to the respiration 

 and the nutrition of the animal, and its structure, 

 adapted to these purposes, affords a striking evi- 

 dence of that marvellous skill which has been 

 employed in the adaptation even of the humblest 

 living creatures to their mode of life and the 



