503 
of the dorsal blastopore border and Rovx, Hertwic, Berraccuini that 
at first it surrounds the blastopore as a ring, according to Kopscn 
there is some truth in both statements, the rudiment of the head being 
found in front of the newly formed blastopore lip, the contiguous 
rudiment of the dorsal parts of the trunk lying round the blastopore 
border in the semilunar stage. This last view is more and more 
accepted by later investigators (H. V. Winson, 1900, 1902, Kine, 1902, 
Ikepa, 1902) and also my experiments confirm it entirely, as will be 
shown. Moreover this result is in complete accordance with what 
might be expected on my theory. The view is gaining acceptance 
that the principal axis of the egg and the longitudinal axis of the 
embryo approximately coincide and that consequently, when the first 
cleavage of the egg separates the left and right halves of the embryo 
(which is so in the majority of cases, see later), the second cleavage 
will not separate rostral and caudal, but dorsal and ventral parts 
of the embryo. Meanwhile opinions still differ very much; thus 
Bracner (1902, 1905) recently has maintained the view that the trans- 
verse headfold originates exactly in front of the spot where the 
blastoporic rim first appears, ie. 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 farther 
than just beyond the vegetative pole. The egg axis “n'est en relation 
avec aucun des axes principaux de lembryon” (1905). 
About the place where the dorsal lip first appears and about 
the extent of ifs progression over the surface of the eve, opinions 
are also rather divergent as yet. Prrücer and Rovx see the 
dorsal blastopore lip originate on the egg equator, Prrücer lets it 
travel a distance of a little over 90°, Rovx of 170—180°, Moran 
and Umer Tsvpa (1884) see it originate + 30° below the equator 
and travel 120°. AssnrronN (1894) and Korsen (1900), with whom 
Ikepa (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°( Kopscn). BERTACCHINI 
(1899) again quite agrees with Roux and estimate the distance 
travelled through a little under 180°. Kine (1902) finds in Bufo a 
displacement of 140° from a point below the equator. EycLEsHymur 
gives no definite data on this point, his opinion would probably be 
in fair accordance with the results obtained by me. 
By carefully watching the marked eggs and by drawing them 
repeatedly the above questions of course can be answered with 
certainty. The results of my experiments for Rana fusca I have 
