BILL AND HAIRS OF ORNITHORHYNCHUS PARADOXUS. 155 
cells (fig. 8), and it coils in a very characteristic manner in the 
neck and upper part of the bulb (fig. 13; in fig. 8 the coiling is 
only slightly marked ; figs. 14 and 15 represent peculiar forms 
in which this character is not present). The coiled duct passes 
downwards into a straight section resembling the gland duct in 
the dermis with which it is continuous below the bulb (fig. 8). 
It was, however, impossible to establish the existence of a 
cuticle to the duct in the bulb, although the inner part of the 
cells immediately round the lumen stained far more deeply 
than the outer part (fig. 11, d’.). 
Immediately below the whole bulb the duct is invariably 
surrounded by a large ganglion containing abundant medul- 
lated nerve-fibres showing Ranvier’s nodes, and large ganglion- 
cells (figs. 8 and 12). This ganglion is surrounded by a fibrous 
sheath which appears to be prolonged from the dermal sheath 
(corresponding to the hair-sac) of the hair-like cylinder. Large 
nerves are seen entering the ganglion, the sheath of which is 
continuous with their epineurium (fig. 8). The duct which 
pierces the ganglion is separated from it by a distinct fibrous 
sheath, clearly shown in transverse section (fig. 12) but very 
thin in the longitudinal (fig. 8). This sheath appears also to 
be derived from the layer corresponding to the hair-sac, and to 
be continuous with its inner part, while the ganglionic sheath 
is continued from its outer (fig. 8). This, at least, appears to 
be the probable interpretation of the appearances represented 
in fig. 8; but the whole structure of these hair-like epidermic 
cylinders, and the nervous tissues evidently associated with 
them, is so remarkable and complex that the fresh tissues are 
required for their satisfactory elucidation and for the discovery 
of the nerve terminations which we must believe to exist in 
connection with the apparatus. 
I believe that this account represents all that can be ascer- 
tained by the careful examination of the available material, 
and that it supports the conclusion I suggested in 1884—that 
the gland ducts of the bill reach the surface by entering the 
bulbs and by advancing along the medulla of shortened and 
degenerate hairs. Such an opinion is further confirmed by the 
