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LETTER V. 



THE SHELL CONSIDERED IN ITS RELATION TO OTHER 



ANIMALS. 



The mollusk or snail is dead, — and you naturally conclude 

 that the shell, having, served the purposes of its legitimate 

 proprietor, has now become a useless thing in its relations to 

 the animal kingdom, left, like other organized fabrics, to 

 decay and moulder into dust under the operation of the ele- 

 ments to which it is exposed. It was formed for a single 

 specific use, — to cover and protect its native architect, — and 

 being admirably adapted to that use under many variations 

 of structure, the design of its creation would appear to have 

 been attained ; but the designs of divine wisdom are not so 

 narrowly limited, and we find that in the formation of shells 

 the wants of other animals, altogether alien to the first, have 

 been kept in view. As if foreseeing that much time would 

 elapse from the death of the mollusk to the decay of its hard 

 calcareous fabric, and as if unwilling that such a relic should 

 lie useless, the Creator has called into existence certain tribes 

 of animals to possess them during this intermediate time. I 

 do not here allude to a host of worms and zoophytes which 

 find in their sinuous cavities a safe shelter to which they 

 resort as occasion oflTers, but I mean certain crustaceans and 

 worms whose organization makes it evident that they were 

 created of purpose to become the possessors of those exuvial 

 shells, without the protection of which they could not possi- 

 bly exist. One tribe of the crustaceans are called Pea-crabs 

 (Pinnotheres), which pass their lives enclosed within the 

 shells of living bivalved mollusca, more especially of the 

 mussels and pinnae ; and to enable them to do so with safety 

 to themselves, and without inconvenience to their protectors, 

 their bodies are made small, round, and flattened, and the 

 crust is made thin, glassy, and of perfect smoothness, with- 

 out angles or projecting spines. The other tribe arc the 

 soldier or hermit-lobsters (Paguri). The posterior half of 

 the body of this race has no shelly crust, but is covered 

 merely with a delicate transparent skin, and as a compen- 

 sation for this defect, if we may so speak, it is instinctively 

 thrust within some univalve turbinated shell large enough to 



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