THE ARCHIPELAGO OF BREHAT. 115 



This, truly, is an instance of complicated anatomy. 

 We must observe, however, that we have been exa- 

 mining one of the species which approach most 

 nearly to the ideal type of the Annelid. It furnishes 

 a very high term of comparison in the group, and 

 exhibits a very strongly manifested example of the 

 division of labour. Let us now take the Doyerina, 

 which recalls to me the rocks of Chausey. Al- 

 though it is only a few lines in length, our micro- 

 scope will magnify it to several feet, and we shall 

 readily be able to distinguish its organs when en- 

 larged in the same proportion. Well ! here we have 

 a manifest proof of simplification ; the skin is here 

 converted Into a diaphanous covering, the muscles of 

 the trunk are blended into two or three scarcely 

 distinguishable layers ; those of the inter-annular 

 partitions have vanished, and their place is supplied 

 by a simple membrane ; and those of the feet are 

 nothing more than homogeneous cords composed 

 of contractile substance. The dlo-estlve and nervous 

 centres are nearly the same, but their accessory 

 parts have undergone obvious reductions. Then, 

 moreover, the circulatory organs have been reduced 

 to a single dorsal trunk, while the organs of respi- 

 ration have disappeared. Let us next examine this 

 Aphleblna, which was captured amongst the Coral- 

 linas of Brehat. Here the des-radation is still more 



anatomy of the Eunice as perfectly as I could have wished ; the 

 numbers therefore which I have given may vary within certain 

 limits, but they may at all events be regarded as approximating 

 very closely to the truth. 



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