10 On the Origin of Hair and on Scales in Mammals. 
from my previous words (/. c. p. 14) :—‘‘ I do not maintain that 
these scales, as they lie before us, are acquired from the 
Reptiles, but I regard as that which is inherited only the 
capacity of the caudal integument of Anomalurus to form 
such scales.” And further on (p. 19) :—‘* We had come to 
the conclusion that the ‘scales’ of the Manide are structures 
which are to be derived from the scales of Reptiles. From 
our statement it will be clearly seen that we do not regard 
the two organs as completely homologous. The considerable 
difference between the horny scales of Reptiles and those of 
the Manide has indeed already been expressly pointed out. 
But we really believe that both had a common origin... .” 
When, therefore, Romer proceeds to declare that we must 
not, however, forget “that we here have not before us scales 
in their original form,” I cannot apply the admonition to 
myself, if Romer by an “ original ”’ scale means a Reptilian 
one. Now, however, comes the difference, for Rémer goes on 
to write—“ but a secondary scale, which has developed anew 
upon true hair-bearing animals, for that is proved by the 
embryonic hairs of Manis * and Dasypus, and is traceable to 
an adaptation of the skin to the mode of life.” It is conse- 
quently assumed by Rémer that Mammals, proceeding from 
scaly Reptiles, lost their coat of scales, developed hairs, and 
now could obtain scales once more only by adaptation to the 
mode of life, and therefore as a “ secondary new acquisition.” 
In my opinion, however, the primitive Mammals, which 
developed from primitive, scaly, poikilothermic Reptiles, were 
clothed with scales. Behind these scales small and sparse 
hairs at first arose. Whether these were developed by modi- 
fication from smaller scales or proceeded from nerve-end 
eminences which were situated between the scales I do not 
venture to decide. 
With the production of the constant body-temperature 
and of vigorous metabolism, wherein influences of tempera- 
ture must have been decisive, the hairy coat acquired a better 
development, since it protects the body against loss of heat by 
radiation and conduction. With this the integument had 
assumed its special Mammalian character, which also expressed 
itself in the scales, especially in their horny superstructure. 
Indeed I previously designated the difference between the Rep- 
tilian and Mammalian scales as one of the kind that belongs to 
the Reptilian and Mammalian integuments as such. With the 
increase in the number and size of the hairs, which conse- 
* The embryonic hairs of Manis only prove that the hairs are formed 
where they afterwards stand, consequently in always scanty numbers 
behind the scales. 
