CAUDAL AUTOTOMY AND REGENERATION IN THE GECKO 65 
in a foot-note (p. 198) that ‘the attachment of the muscles may 
be the cause of the break in the middle of the vertebrae, rather 
than between two vertebrae’, and this statement (true to 
a large extent), coupled with Powell White’s recent assertion + 
that ‘ there is no special autotomy-site as in the legs of crabs, 
but apparently any vertebra may be involved’ (also true in 
one sense), might very easily convey the impression that caudal 
autotomy is a mere mechanical fracture of any given vertebra, 
with the connected muscles and skin. The whole truth is, 
as Leydig I believe first pointed out, that instead of there 
being only one autotomy plane as in the crab’s claw, there are 
as many autotomy planes, each as complex in form as that 
of the Crustacean, as there are caudal segments. Further, 
I have not yet met with satisfactory accounts of the conditions 
under which autotomy occurs, of the exact modus operandi 
of autotomy, or of regeneration under certain experimental 
conditions, nor with any account of the mechanism by means 
of which haemorrhage is stopped when autotomy occurs, and 
I believe, therefore, that there is justification for describing the 
facts as a whole in the case of Hemidactylus flavi- 
viridis. 
NAKED-FYE OBSERVATIONS ON CaupAL AUTOTOMY. 
(Statement 1) That caudal autotomy is very common among 
Geckos may be concluded from the fact that over 50 per cent. 
of two hundred specimens used in my experiments bore 
regenerated tails, and that it is an easy process may be proved 
by the simple expedient of catching a Gecko by any portion 
of the tail posterior to the unsegmented base ; thus I have 
caught hold of the remaining end of the tail of a young Gecko 
five times in almost as many seconds, and on each occasion 
a portion came off in my fingers. In nature the animals 
usually shed their tails when bitten by other Geckos or other 
animals (e.g. out of twelve perfect Geckos placed together in 
a box on one occasion five had shed their tails within an hour). 
(2) Geckos never shed their tails ‘ spontaneously ’ or from 
1 Vide ‘Report of Brit. Assoc. Advancement Science’, Manchester, 
September, 1915, pp, 472, 473. 
NO. 257 F 
