110 GEO. S. HUNTINGTON 
Didelphis specimen, follows the same plan of bronchial organi- 
zation, with the eparterial but limited to the right lung. 
In comparing these reconstructions with Bremer’s account (p. 
71) and with the diagram of his 12.56 mm. opossum lung (p. 72, 
fig. 10) I am obliged to conclude that the ‘left eparterial bron- 
chus’ deseribed and figured by him is the cranial terminal of the 
first left dorsal bronchus, and that the lungs of Didelphis, as well 
as those of all other marsupials whose architecture has been 
determined, do not depart either in their ontogeny or in their 
adult organization from the pattern found in the dominant pla- 
cental type. Otherwise it would be necessary to adopt the 
untenable view that the uterine embryo of Didelphis develops 
the asymmetrical bronchial anlage, with only right-sided epar- 
terial bronchus, and that in young pouch-embryos between 
10.5 and 12.5 mm. a left eparterial component appears, only to 
be lost in older pouch-young and the adult, thus again restoring 
the primitive asymmetry. ‘This is farther afield than I am will- 
ing to follow the supporters of the Reduction Theory on the evi- 
dence thus far adduced. However, this as well as many other 
questions of intense morphologic interest still await the oppor- 
tunity of studying large and closely graded series of well-fixed 
uterine embryos and early pouch-stages of the opossum. I am 
still in hopes that the rich embryonic material of Dzidelphis 
secured several years ago for The Wistar Institute through the 
energy and skill of Drs. Hartman and Heuser may eventually 
become accessible to qualified American investigators for the 
purpose of definitely answering the important morphological 
problems, the solution of which is locked up in the marsupial 
ontogeny. 
It is of course conceivable, as in the case of d’Hardiviller’s 
publication, that all the individuals composing the youngest 
litter of Didelphis embryos studied by Dr. Bremer possessed an 
aberrant bronchial organization. Against this assumption is the 
fact that cardinal bronchial variants of the adult are excessively 
rare throughout the entire marsupial suborder, as compared 
with the placentalia. Narath (33, p. 326) found no instance of 
the left eparterial (apical) bronchus in 16 representatives of 9 
