162 EDWARD B. POULTON. 
gas bubbles. As in the larger hairs, the shaft passes into a 
pigmentless and, in this case, far more slender base (fig. 18, 
in which the sections of the colourless bases of small hairs 
are seen to be much smaller than the dark circles which 
represent the sections of shafts and upper parts). 
There is no trace of either pigment or medulla in the bases 
of both larger and smaller hairs (see figs. 17 and 18 for 
sections of bases). 
Such is the appearance and arrangement of the groups of large 
and small hairs which apparently cover the whole surface of 
the body and head. 
On the upper surface of the tail the large hairs become stiff 
and bristly, but still flattened. They probably correspond to 
the shields only of the large hairs already described. Passing 
from the back on to the tail the small hairs become short and 
scanty, and towards the tip disappear altogether. The succes- 
sional hair emerges as on the body, and the overlap is the 
same, but the gland duct opens beneath and behind instead of 
in front of the hair. The under surface of the tail in a male 
individual not quite fully grown was covered with short 
flattened large hairs set very obliquely, in fact almost hori- 
zontally. They appear to want the medulla and the hair pig- 
ment. In several full-grown individuals this part of the tail 
was more or less bare, but the bases of large hairs could be 
detected, together with patches of hairs having frayed and 
worn ends. 
The manus and pes, except for the bare palmar and plantar 
surfaces, are covered with hairs very similar to those last 
described, but even shorter. 
Everywhere the groups of large and small hairs, or the large 
hairs alone, appear to be set in irregular rows, transverse to 
the long axis of the body which they clothe. 
3. Comparison between the Hairs of Old and Young 
Animal. 
Very interesting results follow from the comparison of the 
hairs of the mature animal] with those of a young one in which 
