BILL AND HAIRS OF ORNITHORHYNCHUS PARADOXUS. AG 
forms were originally terrestrial and have returned to an 
aquatic life. Now in Cryptobranchus the condition of the 
sense-organ and its relations are very interesting. The epi- 
dermis contains a considerable number of layers, the three or 
four outer ones being horny. The sense-organ at the apex of 
the wart-like papille is oblique to the surface; there is a 
corium papilla below it, on the apex of which the sense-cells 
are grouped. The supporting cells are greatly increased in 
number, and leave only a very narrow channel between them 
leading to the centrally-placed sense-cells. 
After describing these organs, he proceeds to compare the 
various parts with those of a hair. The axially-placed sense- 
cells, having no longer any purpose to serve, have disappeared, 
and with them the nerve; nevertheless, the cells are repre- 
sented by the medulla of the hair. The supporting cells have 
given rise to the cortex; the outermost, or covering cells, as 
he terms them, become the cuticle, while the protecting cells, 
overhanging the sense-organ in Triton, &c., are represented 
by the inner root-sheath in the hair. This gives what in 
Maurer’s opinion is the only intelligible explanation of this 
inner root-sheath. 
In reply to this theory as to the origin of the Mammalian hair, 
Leydig (8) admits that there is no doubt a remarkable similarity 
in the mode of development of the two structures, but points 
out other structures which might with greater probability be 
taken into consideration in dealing with its phylogeny, viz. the 
“ perle-organe ” of certain Cyprinoid fishes and the “ femoral 
glands” of Lizards, which he had previously described (7). He 
rejects a view which he was tempted at one time to hold, that 
hairs may be derived from horny projecting papille on the skin 
of Amphibia which are mere local thickenings of the epidermis. 
Maurer again (c) takes up the cudgels in favour of his theory, 
and describes the results of his own examination of these two 
organs, which he has made with an open mind, putting 
himself, as it were, in the position of a sceptic of his own 
theory. But he finds no reason to alter his previous opinion, 
indeed is strengthened in it: he adduces confirmatory evi- 
