106 GEO. S. HUNTINGTON 
That on the left side is always smaller and slightly lower placed, 
and the air-chambers supplied by it do not form the apex of the lung, 
still in spite of its small size and relatively low position, it is distinctly 
above the first ventral bronchus and behind the artery and so corre- 
sponds to the eparterial bronchus of the right lung, and may be consid- 
ered as making the two lungs symmetrical and reptilian in type, as no 
placental lungs are. 
In the older pouch-stages (14 em.) and in the adult animals 
the opossum-lung is described (p. 72) as changing ‘“‘from the rep- 
tilian to the mammalian also in the loss of the left eparterial 
bronchus.’’ Bremer is unable to state how this loss is brought 
about, owing to the lack of the requisite intervening stages in 
his material. These observations range themselves therefore in 
support of d’Hardiviller’s claim discussed above that in the 
mammal (Lepus) the left stembronchus carries at one stage of 
its development an ephemeral eparterial bronchial anlage which 
during the period of its temporary existence renders the right 
and left lungs symmetrical equivalents. They therefore call for 
careful consideration here, since they constitute the only evi- 
dence confirmatory of d’Hardiviller’s observations which has 
been offered in the entire literature. ‘They hence fall within the 
scope of this paper in a discussion of the Reduction Theory. 
In his admirable account of the development of the lungs in 
the pig published in 1906, Flint (21) considers Bremer’s findings 
from two important standpoints: 
He calls attention (p. 22) to Bremer’s statement that no pla- 
cental lungs are symmetrical in the possession of a bilateral 
eparterial development and quotes in refutation the long list of 
mammalan forms (since materially increased) pub'ished by 
Aeby (2), Narath (33) and myself (25) in which the bilateral 
eparterial bronchus is normally found. 
Flint also questions the accuracy of Bremer’s assumption that 
the bilateral eparterial development is a reptilian character and 
cites a personal communication from Hesser (22) who was unable 
to detect any eparterial bronchial development in his reptilian 
material. Flint concludes his consideration of the question with 
the following statement (p. 116): 
