Ce Ce ee aia ee 
1891.] Embryology. 753 
have yet found in individual varieties of bats. That of the foot and 
of the ear, each 4 mm., is great for so short organs. The difference 
in tragus, 3.5 mm., particularly strikes the attention. I am inclined 
to believe that this is the least variable organ in bats. 
Notwithstanding these differences the closeness of these two bats is 
very marked, and I should not be surprised if azor should eventually 
prove to be but a variety of senex. However, until there is positive 
evidence that such is the case, it is advisable to consider it as a separate 
species, : 
The collector failed to note the date of capture, but informs me that 
he is certain that it was in July or August, and probably in the former 
month. From this I imagine that the young bat would have been 
born some time in September. The specimen was taken at night while 
flying about a bonfire.—HENRY L. Warp, Tacubaya, D. F., Mexico, 
April 20th, 1891. 
EMBRYOLOGY.! 
Some Notes on the Breeding Habits and Embryology of 
Frogs.—The following notes are the outcome of several years of ob- 
servations on the breeding habits and stages in the development of frogs. 
They are confessedly very incomplete, having been collected rather as 
an amusement than with any desire to increase our present knowledge 
of amphibian embryology. Some older observations have been 
verified, and I believe a few new observations made which perhaps are 
worth recording. From many points of view I think the develop- 
ment of the frog is better adapted to the need of students beginning 
the study of embryology than the classical chick. Certainly this 
seems to be true if a clearer knowledge of the phenomena of develop- 
ment in general is desired, and not merely an introduction to human 
embryology,—the best excuse offered for presenting the hen’s egg and 
chick, with its mystifying yolk and white and its incomprehensible (to 
the beginner) larval membranes. On the other hand, the ease with 
which the young chicks are to be obtained at all seasons makes a very 
strong argument in their favor. Correspondingly, the difficulties of re- 
moving the youngerstages of the frog’s egg from the surrounding jelly has 
been a great drawback to its study. Appreciating this last difficulty, 
I have experimented for several years on methods of removing these 
1 Edited by Dr. T. H. Morgan, Johns Hopkins University, Baltimore, Md. 
