CAUDAL AUTOTOMY AND REGENERATION IN THE GECKO 85 
and ventrally and thick laterally, and as usual lined internally 
by a thin dense layer of connective tissue ; it shows no signs of 
lines of cleavage, being continuous the whole length of the tail. 
Internally to the fat layer is the muscle layer, consisting of 
from twenty to thirty (in different specimens) slender muscle 
bands, separated from each other by a corresponding number of 
radiating connective tissue septa (continuations of the dense 
connective tissue lining of the fat layer which extend inwards 
through the fat band to the similar, and here thick, connective 
tissue investment surrounding the axial cartilagimous tube 
enclosing the regenerated spinal cord) and running in a straight 
line the entire length of the regenerated tail (Text-fig. 4, B). 
The fibres of these muscle bands appear to run obliquely from 
the central fat bands outwards to the subcutaneous fat layer 
and have no special connexions in their course, except that 
anteriorly all the bands are attached to the connective tissue 
septa bounding the hind ends of the muscles of the base or 
other portion of original tail. In autotomy the separation of 
the regenerated tail from the part in front of it must be solely 
effected by the contraction of these longitudinal muscle bands 
away from their connective tissue junction with the last 
intermuscular septum, this forcible separation causing the 
simultaneous separation of the slender junctions of the other 
organs. In other words, the tail being seized and held, these 
muscles contract, and since the whole body cannot be dragged 
back, the mevitable result is the separation of the tail. 
Between the layer of muscle bands and the axial tube 
enclosing the regenerated spinal cord lies the substance of the 
submuscular fat bands already mentioned; these are con- 
tinuous from end to end of the tail (cleavage planes being 
cc =calcified cartilage at periphery (the tube is also calcified on 
the inner edge); cr=cartilaginous tube; Nc=extension of 
spinal cord; oc=unealcified cartilage; Ppco=pigment cell. 
D. Longitudinal section of the spinal cord extension in the 
regenerated tail ( x cir. 580). cc=canalis centralis; Rr = Reiss- 
ner’s fibre. E. Section through autotomy plane in the region of 
the fat bands( x cir. 250). The hyaline septum is shown, bordered 
by connective tissue cells, outside which lie the fat cells. Similar 
hyaline septa extend through the vertebrae, muscles, and skin. 
