178 EDWARD B. POULTON. 
dence and launches other arguments against the feather-hair 
theory. 
Still more recently, Emery (15) has given in a preliminary 
note another view as to the origin of hair, promising further 
details later, Hairs are not homologous with scales and 
feathers, but all three are descended from the placoid scales of 
fishes by the substitution of horny material for bony substance. 
In other words, the horny part of these structures in the 
higher animals represents the enamel, and the underlying 
papilla (whether ossified or not) represents the basal (cement) 
plate of the placoid scale. Starting with this assumption, for 
which he at present brings forward no justification, he seeks to 
show that he is supported by the relation of the hairs to the 
scales in the scale-bearing mammals, for he finds, as did Romer 
for Dasypus, that hairs arise on the papillz or forecasts of 
scales, and not between them, as Weber believes. In cases 
where hairs are, in the adult, situated between scales (as on 
parts of the body of Dasypus, Chlamydophorus, and other 
mammals) Emery supposes that the scales which originally 
bore the hairs have been crowded out of existence by the 
greater development of neighbouring scales, which in their 
turn may lose the hairs; these, however, may commence to 
develop, as Romer has shown in the case of Dasy pus. 
With reference to the “scales” of certain mammals (Manis, 
Dasy pus) it has been stated, though without sufficient founda- 
tion, that they are “ fusions of hairs.” ‘There is, however, not 
the slightest foundation for this view, as Max Weber (13), 
Romer (12), and others have pointed out. They are true scales, 
similar to those of reptiles! and having a similar developmental 
history, the chief difference being the shedding of the scale in 
reptiles and its permanence in mammals. Both the above- 
mentioned writers agree in regarding the scales and hairs as 
different structures. Thus Romer says, “ Hairs have nothing 
whatever to do with scales ;” whilst Weber, in a later paper 
(14), hesitates to adopt either Maurer’s view or the earlier theory. 
Weber, however, regards the scales of Manis, those on the tail 
1 Davies, however, denies this. 
