30 BENNET M. ALLEN 
sions, although differing from Dr. Allen’s in details of early dis- 
tribution and periods of migration, uphold his.”’ 
Rubaschkin (’08 and ’09) in a couple of recent papers, has 
shown that the sex-cells of the rabbit and guinea-pig are first to 
be found in the entoderm at some distance on each side of the 
hind-gut and that they follow a path almost identical with that 
followed by the sex-cells of Chrysemys. These references to the 
coincidence of the views of other recent writers with my own are 
made to show that I do not stand alone in placing emphasis upon 
the entodermal origin of the sex-cells in the vertebrates. At the 
same time I wish, however, to disclaim any intention of making 
at this time a sweeping claim that the sex-cells of all vetebrates 
arise in the entoderm. Wheeler’s work on Petromyzon (99) 
shows that they may be included in the mesoderm at the time 
when that layer is split off from the entoderm. He has, however, 
pointed out their similarity to the entoderm cells and their dis- 
similarity to the mesodermal cells among which they lie. 
I do not seek to discredit the work of Dustin upon the sex- 
cells of Triton; although his statements about the origin of the 
sex-cells in Rana and Bufo strike me as being very far from the 
mark, because they are so radically at variance with not only 
my own observations, but with those of King and Kuschake- 
witsch as well. Dustin, in his attitude toward the work of others, 
seems to consider that there must be a strict uniformity in all 
forms in both the place of origin and in the movements of the sex- 
cells. He has apparently studied this problem first in Triton 
and at some length. His results, probably correct for that form, 
he has attempted to apply to Rana and Bufo as well, undeterred 
by the difficulties to which attention was called above. Dustin 
is quite ready flippantly to dismiss my work upon Chrysemys, 
because the results there expressed did not coincide with the 
views that he had formed regarding the origin of the sex-cells in 
Triton, Rana, and Bufo.! The process of migration through the 
entoderm is so clear in Chrysemys, that it is unmistakable. 
The sex-cells are not only characterized by their larger size, 
1See postscript. 
