GECKONES 



505 



(p. 512), the skin of the sides of the body and tail is produced 

 into a series of lobes and flaps, the object of which seems to 

 assist adhesion. Many, perhaps the majority of Geckos, have ad- 

 hesive digits, by means of which some kinds are enabled to climb 

 absolutely smooth and vertical surfaces, for instance a window- 

 pane ; or, what is more startling, they run along the smooth, 

 white-washed ceiling, back downwards. The apparatus is com- 

 plicated in its minute detail, but is very simple in principle. The 

 adhesion is effected neither by sticky matter, nor in the way 

 described in the Anura (p. 187), but by 

 small and numerous vacua. The under 

 surface of each digit is furnished with 

 many transverse lamellae. The pressing 

 down of the foot upon a smooth surface 

 causes the lamellae to spread asunder and 

 to drive out the air ; partial retraction 

 lets them return to their original position 

 by virtue of their elasticity ; and little 

 vacua are produced. Each lamella is 

 further beset with tiny hair-Hke ex- 

 crescences, which secure adpression to 

 even the slightest irregularity of surface 

 and at the same time enhance the elas- 

 ticity of the pads. The arrangement of 

 the lamellae and pads differs much in 

 the various genera. For instance, the 

 lamellae are either broad and entire, or 

 they are divided into two parallel rows, 

 with or without lateral hairy fringes ; 

 of the digits is granular, but strongly fringed ; or the lamellae 

 are restricted to the dilated tips of the digits, etc. The fingers 

 :and toes are mostly furnished with sharp, curved claws, and 

 these are in many cases retractile between some of the lamellae, 

 or into a special sheath. Those Geckos which live on sandy, 

 barren ground are as a rule devoid of adhesive pads, the digits 

 being narrow. The typically padded, adhesive digits cause a 

 peculiar sensation when a Gecko hangs on to one's finger, and 

 this feeling has perhaps given rise to the erroneous notion of 

 stickiness. 



The tail exhibits many kinds of shape and size. Mostly 



Fig. 119. — Ptychozoon homalo- 

 cepliahwi. A, Ventral view 

 of the right hand. X 2. 

 B, Side view of a finger to 

 sliow the peculiar arrange- 

 ment of the claw -bearing 

 joint. 



or the under surface 



