670 THE AMERICAN NATURALIST. [VOL. XXXIII. 
teeth no superficial germs such as Röse has described in the croco- 
dile were met with, but al! germs were, as in the higher vertebrates, 
deep-seated. In lizards, as in mammals, a dental ridge is formed; 
this gives rise to a double row of germs, from which the zigzag row 
of teeth in the adult are produced. The palatine teeth, occasionally 
found in the lizard, are probably formed from detached germs of this 
ridge. In snakes the roof of the mouth has on each side two parallel 
rows of teeth. The origin of these two rows was studied to ascertain 
whether they came from the same or separate dental ridges. At an 
early stage the snake possesses a single dental ridge corresponding 
to the outer row of teeth. Somewhat later two ridges are present, one 
for the inner and the other for the outer row. From lack of material 
the author was unable to determine whether both ridges came from 
the single original one or were formed independently. The dental 
ridges eventually break up and form small “ epithelium nests,” from 
which the germs of the later successional teeth develop. G, H, pP, 
The Digestive Tract of the Cat. — The morphology of the digest- 
ive tract of the cat has been carefully investigated by Dr. Franklin 
Dexter.’ Most of the work was done by the dissection of properly 
hardened embryos, a method much more expeditious and certain than 
that of reconstruction from sections, but applicable, of course, only 
to the larger specimens. Dr. Dexter, however, is to be congratulated 
for having succeeded in dissecting embryos which in the hands of 
many would have been consigned to the microtome. 
At early stages much of the large and small intestine of the cat 
is contained, not in the body cavity proper, but in the extension of 
this space into the umbilical cord. This condition has already been 
observed by Mall in the human subject and in the pig, and has also 
been identified by Dr. Dexter in the dog and the rabbit. It may be 
generally characteristic of mammalian embryos. In the cat, part of 
the liver even may be lodged for a short time in the cord, and the 
excessive growth of the liver is supposed to be the occasion of this 
extra-embryonic migration of the intestine. The return of the intes- 
tine to the body cavity is accomplished in an orderly sequence: first, 
a simultaneous entrance of the two extremities of the intestine; sec- 
ondly, an entrance of the jejunum; and, thirdly, of the remaining 
portion of the ileum. 
1 Dexter, Franklin. On the Morphology of the Digestive Tract of the Cat. 
Reprinted from the Archiv fiir Anatomie und Physiologie, Anat. Abt. Boston, 
1899. 
