SHELLS AND MOLLUSCOUS ANIMALS. 185 



among tlieir matted fronds, masses of shell- fish ; 

 and the remarks which Darwin has made on 

 that wonderful sea- weed, the everlasting bladder- 

 chain, is, in a lesser degree, applicable to others. 

 He observes, that a great volume might be 

 written, describing the inhabitants of a bed of this 

 marine plant. " Almost all the leaves, excepting 

 those that float upon the surface, are so thickly in- 

 crusted with corallines as to be of a white colour. 

 We find exquisitely delicate structures, some inha- 

 bited by simple hydra-like polypi, others by more 

 organized kinds, and beautiful compound Ascidiae. 

 On the leaves also, various patelliform shells, Trochi, 

 uncovered mollusks,and some bivalves, are attached. 

 Innumerable Crustacea frequent every part of the 

 plant. On shaking the great entangled roots, a 

 pile of small fish, shells, cuttle fish, crabs of all 

 orders, sea-eggs, beautiful Holuthurise, Planariae, 

 and crawling nereidous animals of a multitude of 

 forms, fall out together." Life may not be so 

 abundant among our masses of sea-weeds, yet those 

 only accustomed to the use of the microscope, on 

 some of the contents of salt pools, or the objects 

 among the mass of marine vegetation, can form 

 any idea of its abundance in these places. 



The animals of the Conchiferous tribe are head- 

 less mollusks, and are affixed to their valves by 

 muscles which stretch from valve to valve. Shut 

 up in their shelly homes, destitute of organs of 

 vision, and with very limited means of moving from 

 place to place, they can have little communication 

 with objects around them. Many are fixed to 

 the rocks; some, like the oyster, lie in compact 

 beds ; some fasten themselves firmly, like the 

 mussel, to the rock, by means of chains spun out 



