583 



mere pearly scale on the surface of the caput (Introduction 

 p. vii.). The immovability of the eyes of spiders is also 

 noticed at p. vii. (Introduction] ; the varied direction of their 

 visual axis being supposed to compensate for want of power to 

 turn the eyes themselves one way or another. A skilful micro- 

 scopic observer, however, of my acquaintance, in correspondence 

 several years ago, stated that he believed some spiders, at least, 

 possessed a power to direct their vision by a perceptible and 

 voluntary internal movement of the oye. A movement of this 

 kind was noticed in the eyes of a living example of Atypus piceus 

 (Sulz.). My own idea is that there is no such inward movement 

 of any portion of the eye ; the apparent movement being proba- 

 bly caused by the play of light upon some portion of its internal 

 anatomy. I have very recently observed this movement in the 

 two large anterior eyes of an example of Aelurops V-insignitus, 

 "Walek., several days after immersion in spirit of wine, showing 

 that it could not possibly be occasioned by any voluntary 

 inward movement of the eye itself. 



TOUCH AND HEARING. 



The sense of touch, or feeling, is no doubt much assisted by the 

 hairy armature of the logs, palpi, and other parts. It is also 

 probably through these hairs that the sense of hearing is principally 

 exercised. It is certain that spiders are very sensibly affected by 

 sound, though we may not, perhaps, be inclined to credit them 

 with the power of discriminating and enjoying musical sounds 

 which has been attributed to them (Walck., Ins. Apt. 1, p. 110). 

 An experiment like tho following, and one oasily made, strikingly 

 proves the excessive sensibility of spiders to sound. In the 

 month of September, 1879, I was standing a few feet off from a 

 female of Epeira diademata sitting in the centre of its snare, my 

 son Bertie being at a little distance. Having occasion to 

 call to him (in not a very loud voice), I observed a distinct kind 

 of start and tremulous movement in the spider. Repeating my 

 call in a louder tone, the starting and convulsive trembling of 

 the spider were repeated in a more intense degree. We then 



