726 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
organs of Mammals, that it is possible, after previous fixation wit h 
Flemming’s and Hermann’s fluid, and after treatment with acetic acid, 
to demonstrate a large number of varieties of white corpuscles. If we 
take the cytoplasm as our guide we may distinguish three types — 
Lymphocytes, Leucocytes with clear protoplasm, and Leucocytes with 
contact protoplasm. Of these the second and third each gives rise to 
four derivates. The second forms phagocytes with clear protoplasm, 
leucocytes with safranophilous, or with fatty granulations, and mega- 
caryocytes with clear protoplasm. The third gives rise to phagocytes with 
compact protoplasm (the granulations of which may be cytoplasmic, 
safranophilous, fatty, or pigmented), the vacuolar leucocytes, megacaryo- 
cytes with compact protoplasm, and polycaryocytes. Of each of these 
varieties the author gives short descriptions. 
7. General. 
Hairs and Scales in Mammals.* — Herr M. Weber discusses the 
question of the origin of hairs, and their relation to scales. He touches 
upon the wider problem of the homology of scales, feathers, and hairs, 
but chiefly limits himself to the relation of hairs and scales. 
In examining the scales of Manis, Anomalurus, Myrmecophaga jubata 
and tamandua , he found that the method of arrangement differed little 
from that found in Reptiles, and that, although the scales themselves 
were always devoid of hairs, these occurred in greater or less abundance 
behind or between the scales. The number of hairs varied inversely 
with that of the scales, and the arrangement of the hairs depended on 
that of the scales. 
From these facts Herr Weber concludes that all Mammals had 
originally a covering of scales like that of Reptiles, and that these 
primitive scales have persisted, though in a specialized form, in an 
animal like Manis. The presence of scales on the tail only, as in rats 
and mice, is to be explained by the fact that, while a covering of hair is 
important for the body as assisting the maintenance of the high tem- 
perature, it is a matter of indifference for the tail. Recently, Herr 
Weber has been able to confirm and extend his theory. It is found 
that in the vertebrates investigated the hairs are arranged in definite 
alternating groups. In some cases each group contains only three hairs, 
but usually many more. This definiteness of arrangement seems to 
confirm in a most striking way Herr Weber’s view that hairs arose 
while a covering of scales still existed. In cases like that of Myrmeco- 
phaga , where a few hairs are found between the scales, the arrange- 
ment of the hairs is directly related to that of the scales. In Mammals 
which are quite devoid of scales it is again found that the hairs have a 
very definite arrangement. According to the author this justifies the 
view that the definiteness of arrangement was induced by the formerly 
existing scales. 
If this view be correct it leads naturally to the conclusion that the 
scales of such existing Mammals as possess them are specialized 
representatives of the primitive scale-covering of the ancestral Mammals. 
The remainder of the paper is in consequence devoted to the maintenance 
of this view against Romer’s theory that existing Mammals with scales 
are derived from hairy ancestors, that is, that the scales are secondary. 
* Anat. Auzeig., viii. (1893) pp. 413-23. 
