ON THE OKEEN COLOUR OE THE HAIR OE SLOTHS. 337 



On the Green Colour of the Hair of Sloths. By H. C. Sorby, 

 LL.D., E.E.S., F.L.S., Y.P.G.S. 



[Bead April 7, 1881.] 



Some years ago the late Mr. E. E. Alston called my attention to 

 the green colour of the hair of Bradypus castaniceps, noticed by 

 Seemann, who had inquired of Dr. J. E. Gray whether he knew 

 any greeu species of Sloth, for that such was the colour of one 

 living in Nicaragua. Seemann, in a letter quoted by Gray in a 

 paper in the ' Proceedings of the Zoological Society ' *, raised the 

 question whether this green tint, so abnormal in mammals, might 

 not be due to a parasitic alga; and suggested that one reason why 

 the animal was so seldom seen was that the coarse hair, thus 

 coloured, made the creature look almost exactly like a mass of 

 the so-called vegetable horsehair (Tillandsia usneoides), so com- 

 mon on the trees of the district where the Sloth occurs. Little 

 or no further attention appears to have been directed to this 

 question in England ; and neither Mr. Alston or myself had any 

 idea that it had been carefully studied in Germany. On examin- 

 ing, both microscopically and spectroscopically, some of the hair 

 from Seemann's specimen, which had retained its colour where 

 not exposed to the light, and comparing it with specimens from 

 CTiolopus Hoffmanni, I was soon convinced that Seemann's ex- 

 planation was correct ; and after I had devoted a considerable 

 amount of time to this subject, Mr. Alston accidentally found 

 that Welcker and Kiihn had published a very complete memoir 

 on the growth and structure of the hair of Sloths and on the 

 algse parasitic on themf. I cannot therefore lay claim to having 

 been the first discoverer of these organisms, but have worked out 

 the question in an independent and different manner, and observed 

 some facts which are not described in the paper just cited. 



In the first place, I have had the advantage of studying fresh 

 material, and not, like previous authors, merely specimens that 

 had been kept long in museums, which was perhaps the reason 

 why the general green colour of the hair is not alluded to by 

 "Welcker and Kiihn. Early in the year 1877 a Cholopus was sent 

 to the Zoological Society's Gardens direct from its habitat, which 

 died very soon after its arrival ; and Mr. Bartlett kindly placed 



* 1871, p. 429. 



t Abhand. der naturf. Ges. zu Halle, 1866, vol. ix. p. 20. 



