and on Scales in Mammals. 3 
rudiment of the reptilian scale,” we may deduce the following 
conclusions. In the Mammalian integument primary corium- 
papille may first appear which are homologous with the 
scales of Reptiles and are of only transitory duration. Upon 
these secondary but permanent hair-papillaee may develop, 
though never until the formation of the epithelial hair-bud 
has taken place. Hair-rudiments may, however, also be 
formed in the smooth skin. 
The epithelial hair-bud is derived by Maurer from _nerve- 
end eminences, as found in Pisces and Amphibia. In very 
instructive fashion Maurer develops step by step the points in 
which the two organs agree. Finally he shows how, in the 
modification of a specific integumentary sense-organ of the 
Amphibia into a simple sensory dermal organ like hair, a 
change of function must occur. This was probably ushered 
in by the loss on the part of the integumentary sense-organ, 
owing to adaptation to terrestrial life, of its primary sensory 
nerves (which came from the vagus), and the acquisition of 
simple sensory branches of spinal nerves. By this means it 
became a sensory organ of the integument without specific 
character, and capable of further development into the hair. 
A rudimentary Amphibian integumentary sense-organ, 
evincing a tendency towards the formation of corneous matter, 
is indeed a long way from a hair; yet the interval can be 
traversed by the train of thought which sets up the 
hypothesis. 
Greater difficulty is found in arriving at the hairy coat. 
Maurer’s deduction takes the following shape. ‘The aforesaid 
integumentary sense-organs of Amphibia were originally 
distributed in connexion with the ramus lateralis of the vagus 
nerve. In old animals “it is possible to demonstrate a multi- 
plication of the organs, a dissolution of the three rows which 
were originally present. ‘The rows become indistinct. At 
the same time in the groups of organs an indication of the 
formation of rows is still demonstrable.” Further on we 
read (p. 795) :—“ In the arrangement of Mammalian hairs 
also it is always possible to recognize to a certain extent the 
formation of rows. I regard these as vestiges of the regular 
arrangement of the integumentary sense-organs in Amphibia.” 
Upon what this conception is based is not clear. The third 
term of the comparison must, however, be the manner of the 
arrangement of the rows of hairs and of the rows of dermal 
sense-organs. We miss the proof of a similarity in this 
respect. Of the rows of Amphibian integumentary sense- 
organs it was merely stated a few lines before that they 
become indistinct, but that in the groups of organs an indica- 
* 
