Ze, A. A. W. HUBREOCHT. 
by disclaiming the greater number of these cases. I feel 
convinced that in certain of the cases observed Mehnert and 
Mitsukuri have seen what is really the rudimentary plasmodi- 
trophoblast of reptiles, but that in others the first-named author 
has been misled and has confused what is really a superficial 
layer (distantly comparable to a mammalian epitrichial layer) 
of later embryonic phases with trophoblastic elements that 
can only be noticed in certain early phases. I have pub- 
lished this disclaimer more than ten years ago (95, p. 27, 
Anmerkung); I can here only repeat it. A real Reptilian 
trophoblast can, I think, be clearly detected in Mitsukuri’s 
(90) Fig. 59 of Clemmys, where we find a separate cell- 
layer of flattened elements accompanying the amnionfolds 
on their outer surface. This layer is not continued on 
the inner surface of the amnionfolds as Mehnert will have 
it in his case of Emys lutaria. Also in his coloured figures 
(l. c., 830a—37a) Mitsukuri seems to indicate, by a different 
tint of red, that he did not (as does Mehnert) see any con- 
tinuity between this outer trophoblastic layer and the inner 
lining of the amnion. 
If we were to adopt Mehnert’s view—as I have perhaps 
been inclined to do more than I was justified to in 1895— 
then we would have to look not only upon the inner layer of 
the amnion as trophoblastic, but also upon the covering layer 
he describes in the duck, which forms a continuous supra- 
epithelial stratum both on the back and on the ventral 
surface of the embryo; and a comparison with what we have 
above described for the mammals ought to make us diffident 
in accepting this view as the real interpretation.! 
' It must be borne in mind that the phenomena here discussed are as yet 
only very partially known. And if we consider the very various methods 
which we have discussed above (p. 11), according to which the mammalian 
trophoblast disappears above the embryonic shield, we may also expect 
variatious in the Sauropsida. If we suppose that an arrangement like that in 
the rabbit and other rodents (Figs. 15 and 28) where the Rauber Deckschicht 
remains distinct for yet a longish time, were yet further protracted, we 
might obtain a state of things as that which is described by Melnert. for 
Emys and certain other forms, I should not mention this if it were not 
