186 THE AMERICAN NATURALIST. 
cesophageal muscle. These by their contraction draw apart the 
walls of the alimentary canal in this region, and the external 
air rushes in through the nostrils to fill the vacuum thus formed. 
In my previous paper, not having the present point of view, I 
said little about the muscles used in expiration, but it is now 
obvious that the well-developed muscular layer which surrounds 
the pharynx in some of the species, and which I have figured 
in Fig. 2 of the article referred to under the name of pharyn- 
geal muscular sheet, must have that function. It is also prob- 
able that in some species the digastricus pharyngis becomes a 
powerful expiratory muscle. 
Summarizing the results thus far obtained, we may state 
the following: Desmognathus fusca breathes mainly by means 
of a definitely localized portion of the anterior part of the ali- 
mentary canal, which may be known as the pharyngo-wsopha- 
geal lung. The walls of this organ are richly supplied with 
blood from a capillary plexus which is irregularly reticular in 
its pharyngeal portion, and in its esophageal portion consists 
mainly of very numerous longitudinal vessels which run paral- 
lel with the mucous folds. Rhythmic inspiratory and expiratory 
movements of this organ are caused by two sets of muscles, the 
one dilating and the other contracting the lumen. 
These motions are accompanied and assisted by respiratory 
movements of the floor of the mouth, as in other salamanders. 
The mouth is normally closed during respiration, and the nostrils 
are used for the passage of air. The anterior nares are equipped 
with a regulating apparatus, as in other salamanders, and for the 
same purpose. 
Although the above summary rests upon recent investigation 
upon a single species, it is probable that a similar organ exists, 
with some slight modifications, in the other lungless sala- 
manders. The bibliography referred to here merely by the 
author's name is given in full in Bruner's latest article on the 
subject in the Journal of Morphologv, February, 1900, to which 
the reader is referred. 
SMITH COLLEGE, Nov. 16, 1900. 
