Joseph Marshall Flint 5 
apparent discrepancy between the ontogeny and phylogeny of the mam- 
malian lung is that of Moser, 00, who, in studying the comparative 
embryology of the respiratory apparatus in vertebrates, comes to the 
important conclusion that all vertebrate lungs are formed by a common 
growth process. In birds the respiratory apparatus is developed from 
a projection of the head gut, and its bronchial system results solely from 
a process of budding. In reptiles the growth process is exactly like 
that in birds, namely, by a bronchifugal system of sprouts while the 
septa are produced by relatively resistant points in the lung wall remain- 
ing between two of its outgrowing portions. This same method of 
growth, furthermore, is again repeated in a less localized and more diffuse 
form in amphibians where it gives rise, in the first place, to the dilated 
lung cavity, and, later, to the semispherical projections on the peripheral 
wall of the lung. In amphibia, as in reptilia, septa are formed by more 
resistant points in the lung wall remaining between two projecting por- 
tions. 
Any doubts of Moser’s method or results seem to be effectually silenced 
by the appearance of Hesser’s, 05, careful and convincing paper on the 
development of the reptilian lung. MHesser finds the endodermal anlage 
of the reptilian lung appearing as a fold projecting from the head gut 
immediately behind the last gill pouch. This separates from the cesopha- 
gus in a caudocranial direction. From the cranial portion the trachea 
is formed, while the caudal part gives rise to the bronchi. ‘The latter 
grow out as long, narrow tubes, at first in a dorsolateral direction, and, 
later, parallel to the median plane of the embryo. In the lizards, the 
bronchi begin to widen at the lateral side, making a sharp distinction 
between the extra-pulmonary bronchus and the future lungs. In species, — 
however, where there is no extra-pulmonary bronchus, the dilatation 
affects the whole tube. We have then, at this stage, a respiratory anlage 
consisting of a long narrow trachea with two narrow bronchi arising from 
it. These terminate in two enlarged primitive lung sacs. At this point 
the inner surface of the lung becomes complicated by the more rapid 
growth of certain portions of the wall of the lungs by a hernia-like pro- 
duction of buds. This process begins in a cranial portion of the lung 
and proceeds gradually to its caudal extremity until finally a large num- 
ber of buds surround the sac. In Tarentola, the most prominent group 
appears along the dorsal side of the stem bronchus, while the remaining 
sprouts occupy transverse rows alternating with the dorsal series. 
While, in lizards, the stem bronchus is dilated, in turtles (with the 
exception of the caudal end which contains a large lumen) it remains a 
relatively small tube. The bronchi grow to considerable length before 
