THE AMYGDALA IN AMPHIBIA Qk 
Cajal’s name, olfactory projection tracts, and she distinguished 
the dorsal and ventral components of the latter. The relations 
in the frog are in principle identical with those described in the 
alligator, and Miss Crosby’s nomenclature is here adopted. 
The dorsal olfactory projection tract is one of the oldest and 
most conservative fiber systems in the vertebrate brain, having 
long been known and described in various types of fishes under 
the name tractus pallii. 
Larval Anura 
In half-grown tadpoles of the bullfrog, Rana catesbiana, 30 mm. 
long, horizontal sections show a well-formed vomeronasal for- 
mation of the olfactory bulb. The amygdala is clearly recognized 
as an area of neuropil distinct from that of the striatum. In 
sections stained with hematoxylin and erythrosin the related cells 
cannot be separated from those of the striatum and other adja- 
cent parts. The commissure of the amygdalae is large and 
readily recognized and is quite distinct from the decussation of 
the lateral forebrain bundles. The other fiber tracts are not 
revealed by these preparations. 
In the brains of much older tadpoles of this species approaching 
the metamorphosis (150 mm. long), without forelegs and with 
hind legs 65 mm. long, cut in the horizontal plane and stained 
with hematoxylin and eosin, the relations of vomeronasal forma- 
tion and amygdala are essentially as in the adult. The vomero- 
nasal formation is large and very far caudad and is entered by a 
large and well-isolated vomeronasal nerve. The amygdala is also 
large and its neurons are clearly separated from those of sur- 
rounding regions. 
Weigert sections of a slightly younger tadpole of this species, 
145 mm. long without fore legs and with hind legs 35 mm. long, 
show a few myelinated fibers in the tractus amygdalo-habenularis. 
The ‘brown reaction’ reveals the course of the ventrolateral 
olfactory tract clearly and the dorsal olfactory projection tract 
obscurely. 
Our collection contains sections through the entire head of old 
tadpoles of Pickering’s treetoad, Hyla pickeringii. These are 
