CAUDAL AUTOTOMY AND REGENERATION IN THE GECKO 91 
tissue, nerve cord, and other features seen in sections. This 
result is of importance because it proves (1) that regenerative 
cells are present in a part of the body which, under normal 
conditions, never reproduces a tail, and (2) that the peculiar 
characters of the regenerated tail are not due to mere lack of 
continuity with the rest of the organism. The real reason for 
the regenerate tail differing in character from the original tail 
appears to be that the organism as a whole ‘ knows’ that the 
TEXtT-FIG. 5. 
Experimental Regeneration of the Gecko Tail (all figures nat. size). 
A’. Tail regenerated from cut base, after 20 days. A”. Ditto, 
after 43 days. B. Diagram showing direction of cut through the 
middle of an autotomy segment.’ B’. Tail regenerated from cut- 
through autotomy segment (cut B), after 15 days. C. Diagram 
showing direction of oblique lateral cut through one autotomy 
segment. C’. Tail regenerated from the cut C, after 64 days. 
D. Diagram showing direction of oblique lateral cut through two 
autotomy segments. D’. Tail regenerated from the cut D, after 
52 days. E. Diagram showing direction of oblique dorso-ventral 
cut through one autotomy segment. E’, Tail regenerated from 
the cut E, after 67 days. EK”. Tail regenerated from the cut E, 
after 87 days (the tail was shed when held at the point shown). 
E’”, Diagram showing absence of endoskeleton in the lower 
division of the bifid tail of E”. F. Diagram showing direction of 
oblique dorso-ventral cut through two autotomy segments. 
F’. Tail regenerated from the cut F, after 76 days (the tail was 
shed when held at the point shown). G. Diagram showing direc- 
tion of two oblique lateral cuts through an autotomy segment. 
x. Straight tail regenerated from the cut G, after 82 days. 
H. Diagram showing direction of two oblique dorso-ventral cuts 
through one autotomy segment. H’. Tail regenerated from the 
cut H, after 80 days (the tail was shed when held at the point 
shown). J. Diagram showing direction of oblique lateral cut 
through regenerated tail (cf. cut C). J’. Tail regenerated from the 
cut J, after 73 days (the tail was shed when held at the point 
shown). K. Diagram showing direction of oblique dorso-ventral 
cut through regenerated tail. K’. Tail regenerated from the 
cut K, after 73 days. L. Diagram showing two oblique dorso- 
ventral cuts through regenerated tail. L’. Tail regenerated from 
the cut L, after 73 days (the tail was shed when held at the point 
shown). M. Diagram showing position and extent of ventral 
wound made on original tail. M’. Two tails regenerated from the 
wound M, after 80 days. M”. Diagram showing absence of endo- 
skeleton in the lower division of the bifid tail of M’. N. Diagram 
showing absence of endoskeleton in the lower division of a ventral 
accessory tail produced from a wound similar to M, after 80 days. 
B= base of tail; Dc=direction of cut; or=original tail; RT = 
regenerated tail. 
