PULMONARY EVOLUTION IN MAMMALIA 103 
I. Bilateral eparterial type. 
II. Right eparterial, left hyparterial type. 
III. Bilateral hyparterial type. 
3. The left eparterial anlage is not a side branch of the first 
ventral (hyparterial) bronchus. (Narath.) 
4. The bilateral embryonic eparterial anlagen explain the 
human bronchial variations 
It is curious, and somewhat amusing, to find D’Hardiviller so 
carried away by the importance of his own discovery that he 
assigns only a ‘secondary value’ to Aeby’s bronchial types, 
from which his own work derives its chief significance as con- 
firming the prediction made by Aeby seventeen years before. 
But aside from this rather interesting exhibition of scientific 
temperament, the embryological evidence presented by d’Hardi- 
viller would have afforded absolute and convincing proof of the 
correctness of Aeby’s thesis, if substantiated by other observers. 
It is a matter of regret that the astonishing revelations of 
d’Hardiviller, differing from the findings of nearly all other in- 
vestigators who have studied the problem of mammalian pulmo- 
nary development, have not, in the twenty-three years which have 
elapsed since their publication, received the attention which they 
would abundantly merit if confirmed. Narath (33) and Flint 
(21) are the only investigators who have seriously considered 
d’Hardiviller’s claims. The reason for this is to be found in the 
fact that when Narath, in his large monograph, published in 
1901, appeared as the chief supporter of Willach’s (37) Migratory 
Theory, subsequently to be considered in detail (p. 1383), he 
found himself confronted by d’Hardiviller’s observations, which, 
if valid, demolished at one stroke the main contention of the 
theory he supported, and definitely proved Aeby’s hypothesis. 
Narath’s chief publication, embodying the results of careful work 
extending over a number of years (1892-1901), followed so closely 
upon the announcement of d’Hardiviller’s findings, that he could 
not, or at any rate did not, subject them to an independent re- 
vision. He hence naturally accepted them at their face value, 
and so found himself taken at an unfair advantage in meeting 
them. He based his chief argument against the conclusions 
