214 C. JUDSON HERRICK 
accessory bulb. The nervus terminalis is distinct from both 
the olfactory nerve and the vomeronasal nerve, as has been 
clearly shown by McCotter (’13) and others. 
The portion of the olfactory bulb which receives the fibers 
from the general olfactory epithelium is termed by McCotter 
(713) the olfactory formation (regio bulbaris principalis of Gaupp, 
’°99, in the frog); the portion which receives the vomeronasal 
nerve (i. e., the accessory bulb) is the vomeronasal formation 
(Zuckerkandl, 710, p. 11). The latter is usually small, but in 
the turtle (Chrysemys) it is nearly as large as the olfactory 
formation, occupying the entire dorsal surface and upper half of 
the medial surface of the olfactory bulb (McCotter, 717). The 
vomeronasal nerve and formation appear to vary in size in 
proportion to the extent of the sensory epithelium of the vome- 
ronasal organ (Zuckerkandl, 10 a, p. 839). 
In a review of the relations of the vomeronasal organ to the 
respiratory mechanisms of Amphibia, Bruner (’14) has summa- 
rized some of the literature and discussed the functional relations. 
He supports the belief of Seydel that in the higher amphibians 
the nasal organ consists of two functionally and morphologically 
distinct parts; a true olfactory cavity which is used primarily 
for testing the inspiratory current, and an organ of Jacobson 
which receives its stimuli through the medium of the expiratory 
current. His detailed examination of the respiratory mechanisms 
and their functional workings in various amphibians shows that 
this relationship prevails whether the olfactory medium be air 
or water. 
Bruner distinguishes two types of respiration in Amphibia: 
a) In the first the respiratory medium passes freely inward through 
the nasal cavity to the mouth, but its return to the nasal cavity from 
the mouth is prevented by a mechanical valve at the choana. b) In 
the second type the respiratory mechanism is wholly under muscular 
control and the olfactory medium passes freely in and out through the 
nasal cavity. 
Corresponding to these two types of the respiratory mechanism, we 
can distinguish a) Monosmatic forms (single smellers), including 
Necturus and the larvae of Amblystoma and Rana, in which the olfactory 
organ is used to test only the external medium.’ For this condition I 
propose the name monosmesis. b) Diosmatic forms (double smellers), 
