xii GECKONES 



(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 -like ex- 



crescences, which secure adpression to 



even the slightest irregularity of surface 



and at the same time enhance the elas- 



,...,-, , -r,, ,, FIG. 119. Ptychozoon homalo- 



ticity of the pads. The arrangement of cep haium. A, Ventral view 



the lamellae and pads differs much in of the ri s ht hand - x2 - 



jn . _ ,. B, Side view of a finger to 



the various genera. For instance, the s h ow the peculiar arrange- 

 lamellae are either broad and entire, or t of the claw -bearing 

 they are divided into two parallel rows, 



with or without lateral hairy fringes ; or the under surface 

 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 



