THE BAY OF BISCAY. 181 



the interior of its habitation. The Pecten, which is 

 as restless as the oyster is sedentary, possesses organs 

 of vision, and these organs are not placed upon the 

 head, nor are they connected with a brain, but they 

 occupy the margins of the mantle, and derive their 

 optic nerves from the great ventral ganglion. 



These very curious facts were published more 

 than ten years ago in Germany.* I have been able 

 to verify these observations at different times, and I 

 have detected in these eyes in the mantle of a Mol- 

 lusc almost all the parts which are present in the 

 eyes of a Mammal, including even the eyelashes 

 and eyebrows, which are here represented by fleshy 

 cirrhi which surround and protect the delicate organ 

 of vision. Three German naturalists, Grube f , 

 Krohn, and Will, have extended these researches 

 to other genera of Acephalous Molluscs, and they 

 have detected a similar organisation in the Spondyli, 

 Tellings, Pinnae, Arcae, Pectunculi, &c. In the pre- 

 sence of such precise and abundant evidence, our 

 observations on the Polyophthalmians lose their 

 apparent improbability. Indeed, the multiplication 

 of eyes, their lateral position, and their relations 

 with other nervous centres than the brain, are per- 

 haps less singular in this little Annelid than in the 

 Molluscs of which we have just spoken. 



Indeed, as in the case of all animals belonging to 



* The existence of these eyes appears to have been long known; 

 but no detailed anatomical description of them was published until 

 1840. 



f Grube, a professor at Dorpat, has devoted himself, with much 

 success, to the history of the Annelids. He has published several 

 zoological and anatomical memoirs on this subject, 



K 3 



