BILL AND HAIRS OF ORNITHORHYNCHUS PARADOXUS. 157 
gives a figure (pl. 1, fig. 5) showing the grouping of the hairs, 
and points out the fact that the roots of the small hairs diverge, 
that the hairs then converge in the common follicular neck, 
whence they issue in a bundle (p. 69). Whilst Leydig describes 
only four or five hairs in a bundle, Welcker found fifteen to 
thirty of them. 
No author gives any histological details of the structure of 
the hair till Waldeyer (9) in 1884, who only describes and 
illustrates by photographs the difference in the character of 
the medulla and cortex in the various parts of the larger 
hair (pl. vii, figs. 1OO—104). According to him (p. 100), the 
“bristle hairs”? commence basally in a rounded sliaft of mode- 
rate diameter with a thick medulla; then follows a more flat- 
tened but very slender “isthmus,” which further on widens 
out considerably to form the main part of the hair; this 
narrows again at the tip to a point. The isthmus is non- 
medullated, and the medulla of the broad part differs from that 
in the basal shaft. The paper dealing with the skin of Ornitho- 
rhynchus, by Souza Fontes (10), consists of little but quotations 
from Leydig. It contains nothing worth recording. 
These authors give no information as to the bulb, papilla, and 
root-sheaths, nor any other histological details of the hair itself. 
As to the arrangement of the hair, Meijere (11), who has 
recently examined the arrangement of the hair throughout the 
Mammalia, gives a figure on p. 49 showing the hairs on the 
back of Ornithorhynchus in more or less irregular rows— 
the large hairs, represented as round in section, being separated 
from each other by three or four bundles of small hairs: on 
the ventral surface, however, the number of the latter is 
greater. His measurements closely agree with those given by 
Welcker, being ‘048 mm. diameter for the large ones, ‘(008 mm. 
for the small hairs. 
1. BLumrensbacu.—“ Anatomical Observations on the Structure of Orni- 
thorhynchus paradoxus,” ‘ Philosoph. Mag.,’ xi, 1802, p. 366. 
2. Home.— A Description of the Anatomy of Ornithorhynchus para- 
doxus,” ‘ Phil. Trans.,’ 1802, p. 67. 
8. GLtockneR.—‘ Ueber die Haare des Ornithorhynchus,” ‘Isis,’ 1819, 
p- 651. 
