138 Journal of the Asiatic Society of Bengal [N.S., XIX, 
arrangement to the scales on the under surface of the corres- 
ponding digit. At the end of each finger there is a strong, 
recurved claw. The arrangement of the lamellae and the 
shape of the adhesive pads is different in different genera 
of Geckos! but the main feature, e.g. the ridge-and-groove 
pattern appears to be shared by all of them, or at any rate by 
all of those genera in which an adhesive apparatus is present 
on the digits. From the histological account of the disc 
published so far it appears that the minute structure of 
the lamellae is more or oe Similar in almost all Geckos. Ina 
transverse section each lamella is found to consist of four 
chief elements from satsde inwards, (1) a horny layer beset 
with innumerable, branching, setose nd resting 
g 
third element consists of large rectangular cells, with deve- 
loping setose processes in the outermost layer. These are the 
mother-cells of the setose processes of succeeding generations. 
(4) the last layer is the stratum malpighii. e outermost 
layer bearing setose processes is periodically cast off an 
even in the laboratory it can easily be removed with a needle. 
The vacuum theory of the adhesive action of the pads of 
Geckos held sway till 1902 and it was commonly believed that 
“small and numerous vacua 
the lamellae. The explanation, as can readily be seen, was 
similar to that advanced for the adhesive property of the 
cephalic disc of Echeneis or its allies. In the case of the fish 
the raising of the usually recumbent lamellae was a to 
the muscular action on the part of the animal, but n Geckos 
in the following manner: “The pressing down of the foot 
upon a smooth “putince 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.” The same author has, however, 
attributed a small portion of adhesion to the horny, setose 
processes described above, for he says that ‘‘each lam ella 
is further beset with tiny hair-like excrescences, which secure 
pure suction, at any rate, was not the only cause of adhesion. 
Though this ater negatived the suction theory so ably, 
: a cue ea 


oo Faun: Brit. Ind. Rept. Batrachia, Pp. 80-106 (1890). 
? Gadow, Cambridge Nat. Hist. VIII, p. 505 (190 
3 Weitlane:, Verhandl. zool.-bot. Ges. Win, iil, a 328 (1902). 
