182 GEO. Ss. HUNTINGTON 
bronchus and its derivatives, with the exception of the first ven- 
tral hyparterial bronchus ceded to the new cranio-ventral dis- 
tricts. It shows a remarkable regularity in the uniform type of 
its conductory system, and in the bilateral homology of its indi- 
vidual components. The more recently acquired secondary 
cranio-ventral neomorph requires for its organization the de- 
velopment of a new axial conductory canal, occupying within 
the additional territory, however restricted or extended this 
may be, a position strictly analogous to that of the stembronchus 
of the older caudal pulmonary component. Like this it develops 
its ventral and dorsal side branches and its terminal distribution. 
It varies in the extent and arrangement of these elements with 
the varying range and disposition of the pulmonary area under 
its control. It likewise varies in its point of derivation from the 
archeal intrapulmonary bronchial system of its predecessor, the 
primitive lung-stem. The available range of its origin extends 
craniad from the latter’s base. In the initial and lower phases 
of its development it appears as an exaggerated branch of the 
first ventral hyparterial bronchus. As it unfolds and aims at 
the control of a more extended territory this original point of its 
origin proves inadequate, in accordance with the law governing 
the relation between the peripheral expansion of a bronchus and 
the distance separating its origin from the adjacent branches of 
equal rank. The neighborhood has become too crowded, so it 
moves. But it does not carry its old house with it. It selects a 
site in territory less thickly settled and begins to build a new one. 
It does not ‘migrate,’ it ‘emigrates.’ It selects a point on the 
still unoccupied stretch of the stembronchus. If the long estab- 
lished path of the main pulmonary artery supplying the archeal 
system lies in the way, it surmounts it and fixes on a spot be- 
yond, confident in the knowledge that the old stream can be 
tapped to furnish the necessary supply for the new habitation. 
In doing this the bronchus has not only abandoned its ancestral 
birthplace, it also has changed its citizenship. It leaves the 
archeal hyparterial community of its fellows and appears as the 
pioneer founder of the new eparterial colony. The only path for 
still further advance lies open craniad. Depending upon the 
