472 LEON AUGUSTUS HAUSMAN 
the hairs pulled from out the block during the sectioning, a longer 
period in the hot xylene and zylene-paraffin baths was found to 
be the remedy. 
The author here wishes gratefully to acknowledge his indebted- 
ness to the Museum of Vertebrate Zoology of the University of 
California and to the Peabody Museum of Yale University for 
hair samples sent him, and to Dr. G. 8. Miller, of the United 
States National Museum at Washington, and Dr. J. A. Allen, 
of the American Museum of Natural History in New York City, 
both for sending hair samples and aids of one kind and another 
at various times, and for allowing the author the free use of their 
extensive collections of skins. Dr. A. H. Wright, of the Depart-. 
ment of Zoology at Cornell University, lent his kindly aid in the 
determination of some of the vernacular names of species men- 
tioned in this paper. 
Especial thanks are due to Professor H. D. Reed and to Profes- 
sor Simon Henry Gage for guidance and counsel during the 
course of the investigation. 
THE HAIR OF ORNITHORHYNCHUS ANATINUS 
The hair types of Ornithorhynchus (plates 1 and 2) 
The fact that Ornithorhynchus possesses two distinct types of 
hair was made known in 1802, when Blumenbach (1802) described 
its gross appearance. Later Home (1802) recorded the same 
facts. Apparently independently, Glockner (1819), van de Hoe- 
ven (’23), and Peron and Lesseur (’23) made a more careful study 
of some of the structural features, in a general way. A summary 
of the observations up to the year 1825 was made by Meckel 
(26). The relations of the hairs to each other within the follicle 
was the subject of the investigations of Leydig (’58) while the 
size and general gross appearance of the hairs occupied the re- 
searches of Welcker (66). 
The first systematic attempt to review the histology of the hair 
is that of Waldeyer (’84), who was followed in this same endeavor 
by Poulton (94). The latter first clearly indicated the relation- 
