in support of an assertion of Aristotle. b(fi 



Macleay's bare assertion, that the " ocular points" are devoid of 

 the organization requisite to produce vision. 



Now, as these organs, whatever they may be, are manifestly of 

 the same nature throughout the various groups of animals posses- 

 sing them ; and as we cannot, I submit, refuse to credit the con- 

 joint evidence, derived from two very different modes of research, 

 of M. Gaspard and Mr. Bauer, that the organs which crown the 

 larger tentacula of the Helices are not Eyes^ but organs of an 

 exquisite sense of feeling i — may we not conclude that the case 

 is the same with all the Gasteropoda provided with those organs, 

 placed either on their tentacula or directly on their heads ? And 

 may we not refer the assertion of the naturalist of antiquity which 

 we have made the subject of inquiry, to those sagacious genera- 

 lizations, for which his works are now so deservedly esteemed by 

 naturalists ? 



These organs appear to supply the place of hearing as well as 

 of sight to the animals, and perhaps also that of smell. The in- 

 definite language which is employed by M. Lamarck, and by some 

 other writers, when describing them, is unworthy of Science : they 

 may, possibly, have some kind of sensibility of the action of 

 light ; but if they do not possess the peculiar structure necessary 

 to impart to the animals the sensations, either of the colours of 

 outward objects, or of their forms, as manifested by the variations 

 of light and shade, to call them Eyes is a contradiction in terms.* 



* May I be permitted to suggest a hypothetical idea or two on this subject ? 



May not these delicate nervous organs of some of the Gasteropoda and An- 

 nelides correspond to the true Eyes and Ears of animals higher in the scale of 

 animated nature ; analogically representing both, and performing the func- 

 tions of both, in the degree required by the natural exigencies of the animals? 

 As M. Gaspard informs us, that, in the Snail, they have extreme sensibility of 

 the least agitation of the air, is it not probable, that, though not adapted to 

 convey the sensation of sound, they may carry a perception to the sensorium of 

 the animal, of those vibrations of the air which impart that sensation to the more 

 perfect organs of the higher animals ? And, though not provided with the 

 exquisite and complicated mechanism, necessary to produce the varied sensa- 

 tions of light and shade, and of colour, is it unphilosophical to infer, that they 

 may, in like manner, convey a perception of the undulations of the luminiferous 

 ether, which, (adopting the Huygenian undulatory theory of light as revived 

 and explained by Dr. T. Young), enable those animals which possess true 



