Gaspard on Helix Pomatia. 179 



analogous to those which MM. Prevost and Dumas observed to 

 take place, in consequence of the transfusion of blood with sphe- 

 rical globules, into the circulation of animals having blood with 

 elliptical globules. 



§. 22. According to Swammerdam, the two larger tentacula of 

 the Helices, have at the extremity a true eye composed of aque- 

 ous and vitreous humours, a crystalline lens, an optic nerve, the 

 choroid tunic, &c. This naturalist therefore, followed by Lister, 

 Rhedi, Spallanzani, &c. considers them to be endowed with sight. 

 I have made many attempts to elucidate this point, and I must 

 confess that they have all of them proved to me that they are 

 totally devoid of this sense, and in every respect insensible to 

 light, walking and climbing as correctly in the night as by day 

 light. I have found that they do not perceive obstacles placed 

 in their way until they touch them. Deprived of the tentacula, 

 they guide themselves with equal certainty as before. In a word, 

 I find in these pretended optical bodies, nothing more than the 

 organs of an exquisite sense of touch, with extreme sensibility to 

 heat, dryness, moisture, to the slightest shock, or the least 

 agitation of the air; and this arises from a large nerve which 

 is expanded over the extremity. 



They appear also to be deaf as well as blind ; being totally 

 insensible to the most acute sounds, although instantly perceiv- 

 ing the slightest vibration communicated by the foot to the 

 ground. 



With regard to the sense of smell, it is true that we have it 

 asserted on the authority of Swammerdam and Lister, that they 

 are directed by the smell towards cheese placed near them ; but 

 I have never been able to confirm this. In short, I have only 

 been able to ascertain the existence of the sense of taste, and 

 that of touch ; the latter of which they possess in an extreme 

 degree of delicacy. 



(The experiments which Monsieur Gaspard relates on there- 

 production of the parts of Snails, offer no results sufficiently 

 different from those recorded by Spallanzani^ to render it neces- 

 sary to transcribe them.) 



