88 A. A. W. HUBRECHT. 
situated, which is thus normally the first to pass outwards at 
birth (cf. fig. 18). 
When a uterus containing a ripe or nearly ripe foetus is care- 
fully opened by a longitudinal incision, there is seen to be no 
adhesion whatever except in the placentary region (figs. 18— 
21). The uterine walls are stretched to an extreme degree of 
tenuity ; indeed, so thin have they become that even in the 
specimens that were preserved in spirits, and have thereby 
considerably increased in opacity, the limbs, the ears, the 
fingers, and the tail of the foetus can be distinguished through 
this thin layer of maternal tissue. 
Immediately beneath the stretched uterine wall the feetal 
envelopes form a very tight sac containing the foetus. This 
sac is so transparent that in spirit specimens the individual 
hairs on the head, body, and limbs, the nails, &c., can be 
recognised through it (figs. 18 and 47). 
Towards the tail end of the foetus the foetal envelopes pass 
into a button-like projection, which constitutes the placenta. 
Figs. 18, 19, and 47 show this both in the front view and in 
profile ; in fig. 20 the longitudinal section indicates still more 
clearly the way in which the thin foetal envelopes merge into 
the placentary tissue. It is, moreover, visible, both in fig. 18 
and in the longitudinal section (fig. 20), that the placentary 
knob itself adheres with the maternal tissue only along a very 
limited extent of its total surface, viz. a squarish area in which 
numerous lumina are visible (figs. 18 and 47), when the 
placenta is loosened from the maternal tissue by a slight 
shaking. These lumina are formed by the tracts which convey 
maternal blood to and from the placenta. Microscopical 
examination of thin sections through this region reveal without 
any doubt that, indeed, this limited area is the only point of 
fusion, the remaining surface of the placenta being as little 
fused with the maternal tissues opposite to it as are the foetal 
membranes themselves. About the histology and the genesis 
of the placenta of Tarsius I will treat in a later paper; suffice 
it to say that, according to the nomenclature now in use, the 
Tarsius placenta would be directly classed with the discoid 
