EARLY ONTOGENETIC PHENOMENA IN MAMMALS. 265 
where either actual phagocytic attack may be made — Tupaja, 
Ovis, or only a mutual interdigitation may take place — Bos, 
Cervus, the intervening' areas remaining free. 
It has occurred to me to wonder whether the copious flow 
of uterine gland solution in, for instance, the iutercotyle- 
donary areas of Ruminants or the general surface of pigs, 
horses, may not obviate the necessity, so to speak, of the 
trophoblast eating into the maternal tissues by giving it an 
abundant supply of nutritive material. 
I entirely agree with Hubrecht in regarding the Carnivora 
as a central group' with respect to placentation from which 
either cumulate or plicate type could be evolved, or as con- 
necting the two extreme types. Whether the carnivora, or 
the extreme cumulative or extreme plicate is the most primi- 
tive, it is very difficult to say. Hubrecht no doubt makes 
out a strong case for the cumulate type, except that it is 
based upon the non-sauropsidau origin of mammals, which 
seems to me untenable and unnecessary. 
As strong a case might be made out by those who believe 
in the meroblastic egg and the sauropsidan origin of mammals 
for the other view. But, granted that the trophoblast is of 
yolk-cell or hypoblastic origin, I can see little difficulty in 
deriving either the cumulate or plicate type from the saurop- 
sidan meroblastic egg. 
Amnion. 
One part of special interest is the discussion as to the 
origin of the amnion in general and in mammals in particular ; 
and the question as to whether the present condition of the 
Eutherian developm.ent is to be derived from conditions which 
had their origin in a large meroblastic egg, or in a small 
holoblastic type, without the intercalation of a mei’oblastic 
stage. Hubrecht states his conclusions with great perspi- 
cacity in the second footnote to p. 79. 
It seems to me that there is no necessity to give up the 
idea of mammals having been descended from animals with a 
