1910.] Monotremota: Reptilian Characters in the Integument. 145 



1816. De Blaiuville removes them from the Edentates, at first classify- 

 ing them along with the jNIarsupials provisionally in a grand division (p. 7G), 

 but later (1834) formally assigning them to a distinct subclass "Ornitho- 

 delphia" (p. 82). 



1838. Bonaparte applies the name "Monotremata" in Latin form, in 

 a systematic sense. 



1877. Echidna hrnynii Peters and Doria, made the type of a new genus 

 " Aca7ithogIos.sus" by Gervais. Aeanthoglossus being preoccupied Gill 

 substituted Zaglossus and Gervais (later) substituted Proechidna (Palmer). 



Reptilian Characters in the Integument. The Origin of Hairs. 



From a study of the development of the hairs in Echidna, Romer (1898) 

 establishes the probability that the ancestors of the mammals ivere scaly 

 creatures. The following observations are especially important in this 

 connection : 



(1) In certain regions of the body in the young Echidna (Romer, Taf. 

 1, fig. 11) each spiny hair protrudes from the apex of a broadly-triangular 

 scale-like structure. These structures are arranged in transverse rows, 

 which alternate and overlap in a very scale^like manner. They are not, 

 however, regarded by Romer as true scales. 



(2) On either side of the backwardly-pointed tip of the hair-spine two 

 or more small papillae occasionally appear. These Romer interprets as the 

 last vestiges of true scales, which were probably also arranged in transverse 

 imbricating rows and determined the scale-like arrangement of the interven- 

 ing rows of hair-spines. These papillae are composed of the same histological 

 elements as both hairs and scales, but they protude from, and are not sunken 

 into, the surrounding integument. 



(3) The internal basal papilla of the hair-spine itself, instead of being 

 a small bulb in the root of the hair as in higher mammals, extends over half 

 way up the shaft and this fact greatly increases the similarity between such 

 a hair-spine and an insunken reptilian scale. 



(4) Romer believes with de Meijere (1894) and Weber (1904) that 

 hairs have gradually replaced scales. 



The preceding observation of Rcimer naturally lead to the question 

 whether the hairs in the ancestral mamvials may not have arisen mucli as in 

 Echidna, i. e., as flattened S'piny hairs between the scales? 



This hypothesis is consistent with many facts, of which the following 

 may be cited: 



(1) The observations of Poulton (1894) on Ornithorliynchus and of 



