The investigations by Wislocki ('28, '30) and by Wslocki and van der Westhuysen ( '40) of the placenta of Hyracoidea revealed the astonishing fact that these animals, which are classzed as the most primitive living ungulates, have a placenta hemochorialis. This caused Wislocki to consider the possibility of a relationship of the Hyracoidea to the Rodentia.
MATERIAL AND METHOD
Curious whether histological data could support this hypothesis, I asked Dr. Wislocki whether he would kindly give me a preserved specimen. He gave me, graciously, a foetus of Procavia.2 I am very grateful to Dr. Wislocki f o r this precious gift.
F o r the details of the collection and preservation of this material, the reader is referred to Wislocki and van der Westhuysen's recent paper ( '40). The specimen under consideration measured 180mm and was one of those which Wislocki and van der Westhuysen had obtained from MI-. iirthur Loveridge.
1 This paper was not written f o r the USPHS, but was begun a t Middlesex University, Dept. of Veterinary Histology. It has been completed, with the friendly help of Dr. John Venable and Dr. H. W. Ades at Emory University, Dept. of Anatomy.
* It is impossible to determine whether the foetus given me belongs to Procavia habessinica or to Heterohyrax (Procavia) syriacus. It shall be referred to in this paper simply as Procavia.