130 
blastoporic rim first appears, í.e. about the egg equator 
(ROUX's view), that consequently the embryo will lie entirely 
on the lower hemisphere of the egg but that the caudal 
end does not, as ROUX thinks, extend on the other side 
as far as the equator but no further than just beyond the 
vegetative pole. The egg axis “n'est en relation avec aucun 
des axes principaux de l'embryon” (1905). 
Ás to the place where the dorsal lip first appears and 
as to the extent of its progression over the surface of 
the egg, opinions are also as yet rather divergent. PFLÜGER 
and ROUX see the dorsal blastopore lip originate on the egg 
equator, PFLÜGER allows it to travel through a distance of a 
little over 90°, ROUX of 170 — 180°, MORGAN and UME TSUDA 
(1894) see it originate + 30° below the equator and travel 
through 120°. ASSHETON (1894) and KOPSCH (1900), with 
whom IKEDA (1902) in the main agrees, also let it appear a little 
below the equator (according to KOPSCH on an average 25°) 
and move through a distance of 60 — 70° (ASSHETON) to 75° 
(KOPSCH). BERTACCHINI (1899) again quite agrees with 
ROUX and estimates the distance travelled through a little 
under 180°. KING (1902) finds in Bufo a displacement of 
140° from a point below the equator. EYCLESHYMER gives 
no definite data on this point, his opinon would probably 
be in fair accordance with the results obtained by mé. 
Conclusions from pricking experiments, —By carefully 
watching the marked eggs and by drawing them repeatedly, 
the above questions can of course be answered with cer- 
tainty. The animal pole then furnishes the landmark which 
most of the above cited authors did not dispose of *). Î 
have investigated in this way the eggs of Rana fusca, 
Rana esculenta and Amblystoma tigrinum. For both the former 
species | have published my results in two preliminary 
papers (1916). Those for Rana esculenta, however, nee 
certain corrections since further investigations have taught 
me that part of the eggs on whose experiments my conclusions 
were based did not develop in a normal way and showed à 
certain tendency to the “spina bifida’ phenomenon. 
For the sake of convenience 1 begin with Rana fusca tor 
which my results are most complete and reliable and which, 
moreover, holds in a certain way an intermediate position 
1) For the question whether the animal pole en a perfectly 
fixed point 1 refer to a remark made on p. 238 of the foregoing 
chapter. For Rana fusca, at any rate, this may be assumed. 
