768 The American Naturalist. [September, 
The yolk sac seems unusually large, and the tail is comparatively 
long at this period, but otherwise these tadpoles are externally like 
those of Rana and Hyla. 
NATURE AND ORIGIN OF THE WRINKLES. 
If the eggs be preserved during the first segmentation while the 
wrinkles are still present, and then sectioned parallel to a plane tan- 
gential to the superior pole, considerable additional light is thrown 
upon this process of wrinkling. ; 
has been noted in the eggs of other frogs the pigment is gathered 
into a thin surface layer over the superior hemisphere. 
Houssay states that the pigment does not characterize this pole, but 
only happens to be there on account of the coincidence of its density 
with that of the surrounding protoplasm (Etudes d’Embryologie sur les 
Vertébrés, Archiv. de Zoöl. Exper., 1890). However this may be, 
during segmentation pigment appears along the sides of the furrows, so 
that eventually the resultant cells come to have a more or less definite 
pigment layer around their periphery, Houssay accounts for this by 
saying that there is an intimate relation between the activity of the cell 
and the presence of pigment. When the resting cell becomes active 
its granules become smaller, and pigment appears in them as the result 
of chemical action. : 
The presence of pigment, therefore, is the result of an increased activ- 
ity in the cell. 
But Bambeke tells us that “the cortical layer, when it enters the 
interior of the protoplasm, is not entirely employed in limiting the 
spheres of new formation. In fact, I find masses of pigment whose 
presence can only be explained by considering them as debris from the 
cortical layer, which has penetrated into the protoplasm ” (Fractionne- 
ment de |’Oeuf des Batraciens, Archiv. de Biologie, Vol. I, p. 346, foot- 
note). 
An examination of sections of these Chorophilus eggs shows a similar 
occurrence. 
In addition to the pigment layer which borders the first segmenta- 
tion furrow, and which is somewhat thicker near the centre of the 
section, there is also a lunate mass extending downward vertically from 
the superior pole on either side of the furrow (Fig. 39) and in imme- 
diate contact with it. This mass can be traced in the sections from the 
surface layer, in which it has very little area, down somewhat beyond 
the bottom of the furrow, where it spreads out laterally and is lost in 
the surrounding protoplasm. In this particular egg the mass does not 
