BPIDEBS AND MITES. 239 



afford good characters by -whicli naturalists have 

 grouped them in genera. In the Clubiona which we 

 have been examining, they are placed in two nearly 

 straight transverse rows on the forehead ; but as this 

 sui-face is convex, it follows that the axis of every eye 

 points in a different direction from that of its fellows. 

 In Epeira, on the other hand, — represented by our 

 great Garden Spider so commonly seen in the centre 



EYE OF SPIDER. 



of its perpendicular web, on shrubs and in comers of 

 our gardens, — the four middle eyes form a square, and 

 the two lateral ones on each side are placed in contact 

 with each other. 



It is interesting to remark that their arrangement is 

 not arbitary, but is ancillary to the varying instincts 

 and wants of the different kinds. On this subject I 

 will quote to you what Professor Owen says : — " The 

 position of the four median ones is the most constant ; 

 they generally indicate a square or trapezium, and may 

 be compared with the median ocelli in hexapod insects. 

 The two, or the two pairs of lateral ocelli may be com- 



