No.1.} BUDDING IN GOODSIRIA AND PEROPHORA. 197 
sion lens all the sections of these two, and numerous other 
cases, and believe that the connection is real and not ap- 
parent ; and since at a later stage the separation certainly 
becomes complete, the connection cannot be supposed to be 
secondary. I therefore conclude ¢hat the pericardium originates 
Srom the wall of the primitive inner vesicle. 
At the same time, however, I must expressly state what is 
already obvious from the description, that the conclusion rests 
upon a preponderance of evidence; there is certainly some 
evidence against it, and that is indicative of a mesenchymal 
origin of the cells. 
(Since the above account of the origin of the heart was writ- 
ten, Lefevre’s short paper has reached me, in which he affirms 
that the mesenchyme is the source of the heart. I have 
reéxamined my preparations with much care, and must say 
that, although, as my words above indicate, Lefevre’s state- 
ments found my mind in a condition of equilibrium, almost, on 
the point, I am still of the opinion that my conclusion is cor- 
rect, at least for P. annectens. In fact, my more recent study 
has discovered some additional evidence in support of my 
earlier conclusion. For example, Fig. 69 represents a section 
in which, az the focus here shown, as seen under the oil-immer- 
sion lens, it is certain that no interrupting line is present, and 
at 8 is one cell, at least, that is undoubtedly about to divide, 
though I do not stake much on this fact. A circumstance 
connected with another section of this same series is I think 
quite indicative that the Az/age is in organic connection with 
the vesicle. It is this. The outer thin wall of the pericardial 
vesicle has been, in the section referred to, by some means 
artificially broken away from the rest of the vesicle ; yet the 
thickened side next the endodermic vesicle is still as indistin- 
guishably confluent with the latter as in the section figured. 
It seems to me quite likely that a force considerable enough 
to break this wall would have moved the whole pericardial 
vesicle from its contact with the endoderm were its relation 
merely a contact. 
I have found no sections in which at some focuses I cannot 
see the separating line to be uninterrupted ; but, very distinctly 
