394 The Morphology of the Ungulate Placenta in Sheep, ete. 
degenerate uterine epithelium. A direct protoplasmic connection is effected 
between fcetal and maternal cells. 
Extravasated blood fills lacune between the mother and the foetus in the 
cotyledonary areas, in which the shorter villi and the bases of the longer 
villi lie bathed in maternal blood, thus leading up to a condition 
characteristic of the cumulate type. 
The placental connection is restricted during the later period of pregnancy 
to the lower part of the uterus, while the upper parts of the horns become 
specially active in secretion, and even exhibit a general destruction of tissue 
to form pabulum. At birth, a large amount of foetal tissue is left within the 
uterus. 
The anatomy of the Elephant’s placenta at half term and at full term is 
shown to be clusely comparable to that of the sheep. The placenta is essen- 
tially plicate, and its special peculiarities are easily derivable from those of 
the sheep. Its most obvious difference, the zonary as contrasted with the 
polycotyledonary form, is regarded as subsidiary in morphological importance 
to the anatomical and developmental characters. On the eround of 
placentation, the elephant may well be associated with the Ungulata. 
Procavia (Hyrax), which is sometimes classified with the Sub-Ungulata, is 
shown, on the other hand, by its placentation to be in no way associated 
with the Ungulata vera, or with the Proboscidea. It is typically cumulate. 
The zonary form of placentation in this case (Hyraz) is not to be compared 
with any other form of zonary placenta. The placenta of Hyraz, some early 
stages of which are described, is remarkable for the highly diffuse and 
cumulate placentation prior to the assumption of the zonary fori. 
The terms cumulate and plcate are proposed as expressing fundamental 
differences in the behaviour of the trophoblast which give rise to two main 
types of placentation and correspond on the whole to the divisions deciduate 
and non-deciduate, although the Carnivora which have the most deciduate of 
all placentas are probably to oe regarded as plicate rather than cumulate. 
The placentation of the Ungulata shows that that order is more closely 
connected with the Proboscidea, and the Sirenia, and Carnivora, than with 
other groups of mammals, whilst the placentation of the Hyracoidea suggests 
no connection at all with those groups, but is of the cumulate type, and 
resembles more closely the form found in certain of the Insectivora. 

