Joseph Marshall Flint 43 
first appearance of the folding of the lung wings around the heart and 
liver, a process which is naturally directed largely by the form of the 
chest wall and shows another adaptation of the bronchi to the space in 
which they have to grow. As yet, however, the remaining lateral bronchi 
have not developed sufficiently to. bend towards the ventral side of the 
body. On the right side, L. 2 has increased considerably in length, but 
possesses no more branches than the reconstruction of the preceding stage. 
The dorsal inferior branch, however, is considerably longer, and now 
grows distinctly downwards and lateralwards. Owing to the presence of 
Lateral 1, with the Lobus superior above and a consequent lack of space, 
this branch does not grow as rapidly as the relatively unobstructed corre- 
sponding branch on the left side, which, at this stage, is somewhat further 
advanced in its development. V. 2 (Bronchus infracardiacus) passes 
from its point of origin on the ventral side of the axial bronchus between 
L. 2 and L. 3, downwards, ventralwards, and medialwards. It is divided 
into branches of equal size, the first passing somewhat inferior (PI. II, 
Fig. 17, 7) and somewhat lateral, forms the inferior branch of the infra- 
cardiac bronchus in the adult. The other division passing more medial- 
wards, is the continuation of the main bronchus. From the dorsal side of 
the stem, D. 2 (Pl. II, Fig. 18, D. 2) arises and subdivides into two short 
branches, the upper and median of which forms the median branch 
(Pl. II, Fig. 18 D. 2, m) of this trunk, while the other continues 
as the main bronchus. L. 3 (PI. I, Figs. 17, 18 L. 3) passes lateral- 
wards and shghtly dorsalwards and, while considerably longer than in the 
preceding stages, it possesses as yet no secondary divisions. V. 3 on the 
right side is, in this specimen suppressed. It is noteworthy that next to 
Ventral 2 of the right side, this element of the ventral series is most often 
missing, a fact which may easily be accounted for by the hyperdevelop- 
ment of Ventral 2, which does not, as a rule, leave much territory in this 
region to be supphed by a ventral bronchus in this segment of the tree. 
Dorsal 3 (Pl. IH, Fig. 18, D. 3) has grown considerably in size and now 
possesses a terminal bud. The fourth lateral (Pl. I], Figs. 17, 18, L. 4) 
shows a marked growth and is provided with an end bud, while between it 
and L. 5, on the ventral side of the axial bronchus a small projection indi- 
cates the fourth ventral bronchus (PI. I, Figs. 17, V. 4). Immediately 
opposite it, D. 4 (Pl. II, Fig. 18, D. 4), arises as a small bud from the 
dorsal aspect of the axial bronchus, while Lateral 5 (Pl. II, Figs. 17, 18, 
L. 5) originates from the outer side of the stem as a small bud-like pro- 
jection. From this point, the axial bronchus passes downwards and 
terminates in a slight end bud. On the left side, Lateral 2 shows a 
