Zoology. — “On the phylogeny of the hair of mammals’. By Prof. 
P. N. van Kampen. (Communicated by Prof. Wesen). 
(Communicated in the meeting of May 31, 1919). 
In his work on “Die in Deutschland lebenden Arten der Saurier”’ 
(1872) and later on’), in a paper in which he rejects MAURER'’s 
well-known theory on the derivation of the hairs of mammals from 
epidermal sense-organs, Leypie draws the attention to the resemblance 
between the structure of the hairs and the so-called thigh or femoral 
organs of the lizards, which he considers to be a transition form 
between ordinary epidermal proliferations and hairs. 
Less attention has been paid to this remark than it would have 
deserved. For the structure of the afore-mentioned organs, whose 
function is not known (they probably participate in the act of copu- 
lation) closely resembles in fact the structure of a hair in a sim- 
plified form *): they are cylindrical rods, composed of horny epidermal 
cells, and sunken into a follicle of the skin. They differ from hairs 
principally by the absence of a cutis papilla and by the fact that 
they do not show a differentiation in medulla, cortex and cuticle. 
It is true that according to Maurer *) they are composed of two 
kinds of cells, but the arrangement of these cells is quite different 
from the one of the elements of the hair. 
As not one of the hypotheses which try to derive bairs from 
epidermal organs of lower Vertebrates and among which the afore- 
mentioned one of Maurer, based on a large body of facts, is best 
known, has been generally aknowledged (indeed, Borrzar *) in his 
review on these theories comes to the conclusion that none of them 
can be maintained and that the hairs in the mammals independently 
have taken their origin in the skin) it is desirable to examine, 
whether the idea uttered by Lieypie might contain perhaps a germ 
of truth. Against a direct derivation of hairs from femoral organs 
it may be advanced that these organs among the recent reptiles 
1) Biol. Centralbl., XIII, 1893. 
*) LEYDIG compares them, in my opinion wrongly, to a bundle composed of 
hairs glued together. 
5) Die Epidermis und ihre Abkömmlinge. Leipzig, 1895, p. 212 ff. 
4) Anat. Anzeiger, XLVII, 1914/15. 
