STUDIES IN MAMMALIAN EMBRYOLOGY. 353 
Wirzburg Congress. Nor does Duval fail to point out the 
identity of the process, such as it is here described by van 
Beneden for the bat, with that which he himself has indicated 
in the Rodents. 
The corrected statement of van Beneden’s views, that is 
contained in Masius’ paper above referred to, does not 
materially differ from the one just noticed. Here, as in a 
later portion of the letter to Duval, it is proposed by him 
to call the outer protoplasmic nucleated layer of epiblast, 
plasmodiblast ; the deeper cylindrical layer, cytoblast. But in 
neither of these preliminary notices is a reason given why the 
name of trophoblast, which I had proposed six months before 
to confer on this layer of epiblast which takes such a consider- 
able part in the process of placentation, should be superseded 
by the new names of plasmodiblast and cytoblast. The only 
reason I can see is this, that in the case of the bat, the tropho- 
blast may be seen for a very long period to consist of these two 
layers that can be easily distinguished from each other (vide 
Frommel’s magnificent illustrations), and for which it may be 
of some advantage to have two distinct names. But I maintain 
that the name of trophoblast should stand for the whole of this 
foetal contribution to the placenta, more especially because in 
Rodents the distinctness of two separate layers has been 
noticed only as a passing phase in the rabbit by Masius, and 
has not as yet been noticed or figured for other genera by 
Selenka or Duval. In the hedgehog there is no such dis- 
tinction, as may be concluded from the text and plates of 
this memoir. On the other hand, the comparison of the 
different elements and layers that enter into the composition 
of the placenta, both of bat and hedgehog, can be carried to a 
most satisfactory length, as I will demonstrate in further 
reviewing Frommel’s figures. 
I must first, however, correct a statement of Masius, which 
would seem to imply that I had overlooked the presence of two 
distinct layers in the trophoblast of the hedgehog. If I had, 
this might be looked upon as an argument to prefer the more 
complicated nomenclature of van Beneden to my own. Against 
