Chap. I. THEIR SENSES. 29 



notion of the form of an object. Of all their 

 senses that of touch, including in this term 

 the perception of a vibration, seems much the 

 most highly developed. 



In worms the sense of smell apparently is 

 confined to the perception of certain odours, 

 and is feeble. They were quite indifferent to 

 my breath, as long as I breathed on them very 

 gently. This was tried, because it appeared 

 possible that they might thus be warned of 

 the approach of an enemy. They exhibited 

 the same indifference to my breath whilst I 

 chewed some tobacco, and while a pellet of 

 cotton- wool with a few drops of mille-fleurs 

 perfume or of acetic acid was kept in my 

 mouth. Pellets of cotton-wool soaked in 

 tobacco juice, and in millefleurs perfume, and 

 in paraffin, were held with pincers and were 

 waved about within two or three inches of 

 several worms, but they took no notice. On 

 one or two occasions, however^ when acetic 

 acid had been placed on the pellets, the worms 

 appeared a little uneasy, and this was 

 probably due to the irritation of their skins. 

 The perception of such unnatural odours 

 would be of no service to worms ; and as such 



