GASTEROPODES. 321 



cannot speak with confidence of their true character. Some are dim or 

 obscure from the interception of vapour, clouds, or films, lessening their 

 distinctness to the eye. 



All bear a general resemblance to each other, without betraying the 

 precise action of any single member. 



Thus it would be vain for us to reason on what they are, or what 

 may be their use and purpose. The whole body is susceptible of some 

 contraction within the shell, and of some protrusion beyond it. All are 

 endowed with vigorous locomotion, all contract, decay, and disappear, 

 and leave incredible multitudes of whitened, spiral, wide-mouthed shells 

 behind them. 



As regards these general facts there seems to be no illusion ; they 

 are daily verified. 



The whole Nautilines contained in any mass of spawn are not pro- 

 duced at once. It is evident that the requisite degree of maturity is 

 progressively attained. The life of all is short, and having escaped from 

 confinement, they speedily perish. 



It is extremely probable that, notwithstanding the preceding gene- 

 ral conclusions regarding the reciprocal resemblances of these beings, and 

 the form of their shells, many discrepancies and distinctions would be 

 discovered by patient investigation. 



Through the medium of the Doris we have been rendered familiar 

 with the Nautiline, but it does not appear that this minute being is by 

 any means peculiar to the tribe. There is reason to conjecture that a 

 similar animal is seen in an early stage of many others. 



Drawings of the different Nautilines have been very carefully exe- 

 cuted, both as complete and of the shells only. But no great difference 

 is to be recognized among them. Artists seldom coincide exactly in their 

 representations of very minute objects. 



But it must be owned that these objects are not seen with sufficient 

 plainness and distinctness. Thus, the few remarks to be made on the 

 subject, are intended simply for the purpose of attracting attention. 



Let us remember what occurred with the Murex antiquus, one of our 



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