298 A. A. W. HUBRECHT. 
will be able to judge whether they do not facilitate both 
the understanding of and the discussion about developmental 
phenomena that are complicated in themselves. It may give 
rise to an increasing confusion if we continue to apply to the 
Mammalia terms that may yet do good service in the domain of 
the Sauropsida, but that cannot be rigorously applied to their 
hairy and suckling descendants. ‘There is all the more reason 
to discontinue the use of many of these terms because of the 
different use that has been made of them by successive authors. 
In an appendix to this article the nomenclature will be more 
fully tested in comparison to what is at present current. It 
will then be seen that I have only introduced it where it was 
strictly necessary. 
The first new name of which I want definitely to establish 
the significance (it was first used by me in the ‘ Anat. An- 
zeiger,’ vol. ili, p. 511), is the name trophoblast. I propose to 
confer this name to the epiblast of the blastocyst as far as it 
has a direct nutritive significance, as indicated by proliferating 
processes, by immediate contact with maternal tissue, maternal 
blood, or secreted material. The epiblast of the germinal area 
—the formative epiblast—and that which will take part in the 
formation of the inner lining of the amnion cavity is, ipso 
facto, excluded from the definition. Even when the layer as 
such may be very passive (e. g. the Carnivora!) the use of the 
name trophoblast will render unnecessary such circumlocutory 
expressions as “ outer epiblastic layer of the blastocyst,” “ pri- 
mitive exochorion,” &e. 
And so, referring back to the hedgehog, which we have just 
been investigating more fully, we can speak of the trophoblast 
at very early stages. When once the polar knob, which will 
partly develop into the embryonic epiblast, has become distinct, 
the divisions of the epiblast into a formative and a nutritive 
1 During the correction of this memoir 1 see from a paper by Heinricius 
on the dog’s placentation (‘ Arch. f. mikrosk. Anatomie,’ vol. xxxiil, July, 
1889), that this author is inclined to attribute very direct phagocytical pro- 
perties to the outer layer of trophoblast cells in that Carnivore. The name 
of trophoblast would then be eminently appropriate even for this order of 
Monodelphia. 
