\CEA. 17 



11. Thence tlcs tin- .-hell originate in tin- ovum, nr it nui^bc coev.il 

 with the irerm itself; and it accompanies the incn incut of tin- animal 

 until liberated by l>irtli. Nor docs its tenuity expo-e tin- structure de- 

 iini'd as a protection for tin- tenant, \vhicli all'ords the most interest i ML' 

 form* employed for tin- mysterious office of sustaining life 

 .uxl advancing increment. 



But the orL'inatiiii: shell is not an exact type of its perfect and 

 .I'inl' it is often more rmlo and shapeless. Herein it corresponds 



with the originating animal, l.oth are gradually refined into stronger 

 resemblance of the product as matured by age. 



The covering U progressively consolidated by new depositions, and 

 it lose* it** early transparency, which has been no useful to the observer. 



licceasions augment the obscurity, and at length interception of this 

 product with a superabundance of calcareous matter, altogether intercepts 

 the view of the animal. 



The safety of the animal is at last entirely dependent on the integrity 

 of the shell. But it can repair many fractures by new secretions, though 

 incapable of a total secretion to protect the body, if entirely deprived of 

 the shell. 



The greatest variety prevails, first in the form of shells ; secondly. 

 in the quantity of matter covering their form. But very little variety 

 prevails among the testaceous animals themselves. I believe that I may 

 affirm, that by far the greater part of shells belongs to an animal related 

 to the Limax, or identically a Limax, and to animals with strong analo- 

 gies to the Ascidia. Besides these, some others are found to be occupants 

 of sheik, whose history is leas explicit. Where the position of genera or 

 species is so much a matter of opinion, alteration and great modifications 

 may be expected. It seems to be the same with the Testacea as with the 

 Zoophytes: the animals inhabiting each exhibit little disparity, while 

 their dwellings are distinguished by a remarkable variety of formation. 



Trie multiplicity of inorganic infinitely exceeds the variety of organic 

 forms connecting the two. 



Among the animals so definitely recognised as pertaining to the 



ocea, are some which we have distingui.-hud ;us approaching, 1. the 







