Joseph Marshall Flint 45 
terminal bud of the axial bronchus. About opposite it on the inner side 
of the stem bronchus, is an evagination marking the anlage of a bronchus 
of the medial series (Pl. II, Figs. 17, 18, M. 5) like that seen on the right 
side at a similar point on the tree in the reconstruction of the preceding 
stage. Fig. 14 shows a section through the end bud where this element 
is in process of formation. The numerous karyokinetic figures and the 
definite extension of the evagination from the median portion of the 
lumen of the bud (Fig. 14, 8) is clearly shown. This picture, when com- 
pared with the reconstruction and Text Fig. 26, indicates that there is 
no essential difference in the method of formation of these branches of 
the stem. Like the dorsal, ventral, and lateral elements, they are pro- 
ducts of monopodial growth. | 
Following is a tabulation of the derivatives of the bronchial tree at 
this stage: 
TRACHEA. 
Ideally 
(2) DI. 
(33) J2) 
(2) VS. 
(ep 
Right bronchus. Left bronchus. 
1652 ree 
(2) DF. (2) Ap. 
(3) D. 
Can 
WV. 2: 
(2) £. 
ID), Dp. 2. 
(2) MU. (2) M. 
105 8} Ike, ot 
V.3 Vira 
L. 4 L. 4 
D. 4 D. 4 
V.4 vV.4 
5 Ibn & 
M.5 
In a pig 18.5 mm. long (PI. II, Fig. 19, Pl. III, Fig. 20) the trachea 
is only a little larger than in the preceding embryo. It still passes 
slightly ventralwards from the upper end to the point of bifurcation. 
On the right side passing downwards and slightly dorsalwards, one finds 
Lateral 1 (Pl. II, Fig. 19; Pl. III, Fig. 20, L. 1), which divides almost 
at right angles into its main divisions, the dorsoinferior (Pl. II, Fig. 19; 
Pl. III, Fig. 20, L. 1, dv) and ventrosuperior (Pl. I, Figs. 19; Pl. ITI, 
