AT2 JORDAN AND EYCLESHYMER. [Von TX. 
All of our observations tend to emphasize the fact that great 
variation is a frequent occurrence in the early cleavage stages 
of the Amphibian egg. We have found irregularity to be the 
rule, regularity the exception. The appearance of the fourth 
set of furrows almost invariably marks the end of any con- 
stancy whatever in the relative position of the blastomeres. 
(See-e.e., Figs. 3; 4,. 73°13; £0,.24, 25,,.32.)) (Whe anterestime: 
condition discovered by Roux ('83) in the eggs of Rana escu- 
lenta, which enabled him to distinguish right and left sides in 
the sixteen-cell stage, we have not met with in any of the eggs 
we have examined. 
We can, furthermore, attach no great importance to the 
existence of the Po/fucht as formulated by Rauber ('s3). It 
is generally true, we admit, that the furrows do not pass 
through a common point on the upper pole of the egg, but 
occasionally they do (Fig. 15). We believe, consequently, 
that it is premature to formulate such a statement as that the 
furrows “alle suchen den Pol zu vermeiden.” The furrows 
do not ‘‘avoid”’ the pole ; but the mechanical cell-stresses are 
rarely so adjusted that the furrows intersect at the pole. 
There seems no need for a special term — Polflucht — to 
express this fact, since the “shunning” of the pole can hardly 
be a matter of primary significance. 
Some of our observations bear indirectly upon the question 
of the relation of the first cleavage plane to the antero- 
posterior axis of the embryo. In the frog, as shown by the 
researches of Newport, Roux, and others, the first cleavage 
plane coincides with this axis ; in Dzemyctylus (Jordan, '93) and 
in 7riton (Hertwig, '92), on the other hand, the first cleavage 
plane is at right angles to the axis. Our observations seem to 
indicate that this coincidence of the antero-posterior axis with 
one of the first two planes of division, is apparent rather than 
real. If such coincidence have any morphological meaning what- 
ever, it must be in this way, that the derivatives of the cells 
on the right side of the first or second plane go to form the 
cells on the right side of the embryo. Our observations demon- 
strate, however, that the first and second cleavage planes un- 
dergo, even in the earliest stages, extensive torsion. Figs. 19, 
