138 A. A. W. HUBRECHT. 
aspect as during pregnancy, only in the inverted sequence ; 
the uteri with the smallest swelling being the furthest 
puerperial stages. 
In this case the properties of fixation and phagocytosis 
characteristic for the mammalian trophoblast have been able 
to come into play on an extensive scale without occasioning 
any hemorrhage in the mother, even leaving a certain 
pabulum behind of embryonic origin, the digestion of which 
may rather be of some advantage to the mother than the 
contrary. There is some reason to believe this arrangement 
in which there is no question yet of an afterbirth, but rather 
the contrary (hence the name of contra-deciduata) should be 
looked upon as a primitive arrangement. The more so as a 
similar phenomenon has been noticed by Hill in Perameles 
where the allantois, however, is not expelled together with 
the embryo as we saw was the case in the mole, but where in 
addition to the trophoblast the allantois also appears to be 
absorbed by the maternal tissue, thanks to the activity of 
migratory leucocytes described and figured by Hill. Having 
advocated (’95n, p. 118) the archaic significance of the arrange- 
ment in the mole, already before Hill found a similar phe- 
nomenon in a didelphian mammal, I must naturally emphasise 
my original contention after Hill’s discovery in a mammalian 
order which, however much specialised it may have become, 
certainly contains representatives of an old stock. Since 
then the peculiar contra-deciduate characters have been 
noted for Tupaja (to a limited extent at least) by Dr. M. van 
Herwerden (’06). 
In these early types we thus see that maternal phagocytosis 
in the placentary regions keeps pace with embryonic phago- 
eytosis. Nutrition by osmotic exchange has undergone a very 
marked reduction in the Didelphia as was discussed above 
(pp. 100, 115), the genera Perameles, Phascolarctos, and to 
some extent Dasyurus being perhaps yet the last in which the 
earlier arrangements have been preserved. In all the others 
the allantois has in a greater or lesser degree been reduced 
both in size and in amount of extension against the trophoblast. 
