and on Scales in Mammals. 3 



rudiment of the reptilian scale," we may deduce the following 

 conclusions. In the Mammalian integument primary corium- 

 papillas may first appear which are homologous with the 

 scales of Reptiles and are of only transitory duration. Upon 

 these secondary but permanent hair-papillfB 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- 

 te 



