EYES OF MOLLUSCS. 341 



example of resuscitation occurred to a specimen of the desert 

 snail from Egypt, cluouicled by Dr Baird. This individual 

 was fixed to a tablet in the British Museum on the 25th 

 March 1846 ; and on the 7th March 1850 it was observed 

 that he must have come out of his shell in the interval (as 

 the paper had been discoloured, apparently in his attempt to 

 get away), but, finding escape impossible, had again retired, 

 closing his aperture with the usual glistening film ; this led 

 to his immersion in tepid water and marvellous recovery. 

 He is now (March 13, 1850) alive and flourishing, and has 

 sat for his portrait." 



The Molluscs, like the heathen idols, have eyes for the 

 most part, yet see not ; organs of hearing, yet hear not ; 

 nevertheless, unlike the heathen idols, they are endowed 

 with these organs for no "make-believe,'' but for specific 

 purposes. A function there must be, and doubtless a good 

 one ; but we speak with large latitude of anthropomorphism 

 when we speak of the " vision " of these animals. MoUuscan 

 vision is not human vision ; nor in accurate language is it 

 vision at all: it is not seeing, hxit feeling; it is not a perception 

 of obj ects, but a sensation of light and darkness. This does not 

 apply to the Cephalopoda, in which vision seems to be as per- 

 fect as in Fishes ; nor, on the other hand, does it apply to those 

 Bivalves which have no eyes at all, not even " eye-specs." 

 The word Mollusc embraces a vast variety ; and, by way of 

 limitation, the reader must understand that the following 

 remarks are confined to those genera which I have directly 

 studied for the purpose — Doris, Eolis, Pleurobranchus, and 

 Aplysia. In the three first genera the eyes are underneath 



