PULMONARY EVOLUTION IN MAMMALIA 151 
Die Untersuchung der allerersten Anlage vom infracardialen Bron- 
chus ist dusserst schwierig, es handelt sich ja wie bei allen Bronchus- 
anlagen um ganz minimale Vorbauchungen, die mit unseren Hilfsmit- 
teln schwer oder gar nicht zu erkennen sind. Was wir sehen, ist be- 
reits ein alteres Stadium, man miisste noch weiter zuriickgehen in der 
Entwicklung und wiirde dann auf einen bestimmten Zellkomplex kom- 
men, aus dem der Bronchus hervorgeht. Der Zellgruppe kénnen wir 
es jedoch nicht ansehen, dass sie den Bronchuskeim in sich trigt. Ich 
dachte eine Zeitlang, dass man vielleicht durch eine stiirkere Anhdu- 
fung von Kerntheilungsfiguren einen Anhaltspunkt dafiir gewinnen 
kénne, um zu entscheiden, von wo eigentlich die Knospenbildung 
ausgeht. Die Untersuchungen liessen jedoch vollstindig im Stich. 
The above passage, which on account of its significance I have 
quoted in full, really tells the entire story and emphasizes the 
way in which a preconceived idea, tenaciously retained, can pro- 
duce, even in an able observer, a mental attitude approaching 
mysticism. For if a morphogenetic theory depends altogether 
on basic differentiations assumed to occur in such early onto- 
genetic stages that they cannot be seen or recorded, the deduc- 
tions must rest entirely on faith and not on scientific evidence. 
This is carrying theoretical promorphology beyond its justifiable 
limits. 
Narath’s monograph contains a mine of invaluable comparative 
anatomical observations, with beautiful illustrations, based on 
preparations showing the utmost technical skill, and the statis- 
tical information is prepared and compiled most carefully. From 
a scientific standpoint the work suffers from only two draw- 
backs: the author’s desire to demolish Aeby’s results, even in the 
minor details which have no real bearing on the problem, and his 
equally strong desire to establish his view of the ‘apical’ bronchi 
and the principle of ‘migration’ in the architecture of the mam- 
malian bronchial tree. One would like to believe that the gross 
mechanical concepts underlying this theory were employed solely 
as figures of speech, for the purpose of visualizing comparative 
relations, were they not unmistakably intended to be taken lit- 
erally, elaborated with infinite and repeated precision of detail 
in nearly every part of the work, and were it not for the attempt 
to prove their actuality by ontogenetic evidence. 
