TIIE 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 digestive 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 

 Aphlebina, which was captured amongst the Coral- 

 linas of Brehat. Here the degradation 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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