212 



We next come upon an interesting variety of claw, the most 

 beautiful as a microscopic object, of all I am acquainted with. 

 This is to be found in the foot of the spider. Fig. 5. It con- 

 sists of three hooks, two large and one small. The two former 

 are serrated like combs, with regular teeth of equal length, till 

 we come near the attached extremity, where they are much 

 shorter than at the free end. 



The teeth are ten or twelve in number. The small hook 

 differs in shape and size from the larger ; it is much shorter, 

 has a much more abrupt curve, and is furnished with one or 

 two teeth only. 



The intention of this foot is obviously to enable the crea- 

 ture to walk readily upon and amongst its slender threads, 

 which would easily elude the grasp of coarser claws like those 

 of the fly. 



It will readily be supposed that these insects possess no 

 power of walking upon perpendicular plane surfaces. They 

 seem to have no special organ to enable them to do so. 

 Though, however, it is true that the majority of these animals 

 do not possess the necessary adhesive quality, some varieties 

 are capable of doing so. In them we naturally search for 

 some peculiar formation. We search in vain. The feet of all 

 spiders are essentially alike, and the only difference which can 

 be detected is an increased number of hairs upon the leg in 

 those which possess the power of walking against gravity. 



The hairs on this part of the body are not of the hard and 

 bristly kind. They are all soft, elastic, and branched so as to 

 form a tolerably broad cushion when the leg is placed on a 

 flat surface. They are more numerous on the under surface of 

 the tarsus than the upper, and are evidently covered with a 

 glutinous secretion, as may be judged by the quantity of dust 

 usually attached to them. 



A very interesting variety of this form of foot exists in the 

 Ht/drachnuj Pig. 39, a small aquatic insect allied to the spider 

 tribe. Its foot consists of two hooks moving readily by a 

 hinge joint. These the animal can protrude or retract at will. 



