( 1078 ) 
And yet this would have been doubly desirable because of the 
fact. that Prof. Hir, who, in his earlier paper on the placentation 
of Perameles, has so markedly drawn together the Eutheria and the 
Metatheria, finds in the development of Dasyurus grounds for again 
separating the two subclasses more definitely. 
Immediately after having become acquainted with Hix's first 
mentioned paper L felt it my duty to attempt to convince myself 
personally that the differences, just alluded to, do exist and I found 
in Prof. Hra’s laboratory the most hospitable reception and at his 
hands the most liberal treatment, which permitted me to see and 
weigh everything for myself, and even to draw and to model such 
preparations as might seem to favour interpretations different from 
his own. I cannot too highly value this disinterestedness, thanks to 
which the problems involved will all the sooner be brought into a 
light full enough for fellow-workers to draw their own conclusions. 
And so I will here attempt to give a brief survey of the principal 
differences which Hitt has detected between the results obtained by 
him for Dasyurus and my own generalisations. which were chiefly 
based on personal acquaintance with the Kutherian ontogeny. 
There is no doubt that the cleavage phenomena in Dasyurus, up 
to the 16 cell-stage, are decidedly peculiar and that the arrangement 
of the 16 cells in two rows of 8 cells each, fully deserves the 
attention which Hin. has directed to it. The first three cleavages 
seem fo occur constantly in a meridional sense. Only the fourth 
cleavage takes place in a plane perpendicular to the three preceding 
ones; the result being an aequatorial band of two cellular belts, one 
composed of 8 smaller cells (representing what Hi. calls the formative 
half of the blastocyst), one other of 8 somewhat bigger cells (the 
non formative half). 
Hitt is no doubt justified in emphasizing the points of difference 
between this stage and the Kutherian morula. They are the following : 
a. The Dasyurus blastulastage is normally open above and below, 
until (very soon after) both the upper and lower solution of conti- 
nuity will have ceased to exist, thanks to continued proliferation (in 
the direction of the opposite poles) of the cells constituting the two 
belts just mentioned. 
4. The unilaminar blastocyst does not contain an embryonic knob, 
which bas been described by all authors writing on the Eutherian 
blastotecyst, as a group of cells applied at one spot against the 
exterior trophoblast, and which is composed of the cells that will 
furnish the embryonic (formative) ectoderm as well as the whole of 
the embryonic entoderm. 
