1897.] . Hair and Feathers. 775 
If the Mammals be, like the birds, descended from the 
Reptiles then it is natural that we should look for those struc- 
tures which have given rise to hairs in connection with the 
Reptilian integument. On the other hand there are those who 
believe that the Mammals spring direct from some Amphibian 
stock and to these the recent work of Maurer is full of interest. 
Maurer maintains that hair and feathers are not homologous 
structures. The feather, according to his view has been derived 
from the Reptilian scale while hair has arisen from the dermal 
sense organs of the Ichthyopsida as a result of a change in 
' habits and conditions of life. As illustrating his views we 
have copied (fig. 18) one of his figures, a diagrammatic longi- 
udinal section of at 
dermal sense organ 
of Triton after the 
metamorphosis, 
which should be com- 
pared with the dia- 
gram of the structure 
of the hair follicle 
and hair already 
Fic. 13.—Diagrammatic es of a cutaneous apis (fig. a ee 
sa pe baig - kiss persr — hee — letters in each indi- 
n: blood A EE T a 9; Hand: M, çarp Hie E gA 
enle’s layer; hu, Huxley’s layer; np, primary logies recognized by 
Pate a i bg secondary nerves; s, sense cells; sc, Maurer. 
ng cells, x and y, points regarded as homo- 5 
y in fig. 3. Slightly condens- 
logous with x an 
ing his account, Maurer says, that when an Amphibian, 
like Triton after the metamorphosis, takes to the land, the 
supporting cells of the sense organs undergo a process of 
cornification and in this condition they show in the simplest 
form all of the parts of the hair and the hair follicle. With 
the transfer to land, as is well known, the dermal sense or- 
gans lose their original function, itself dependent upon the 
presence of water as a surrounding median. In the axis of 
the hair lies the medulla, consisting of dry incompletely corn- 
ified cells. In these I recognize the modified remains of the 
sense cells? The cortical layer is derived from the horny 
* A view considerably different from those earlier advanced by him. 
