504 
combined in a single figure, obtained by the combination of many 
other figures, two drawings being each time superposed and held 
up to the light, the details of one figure being in this way trans- 
ferred to the other. 
The eggs marked at the animal pole teach us what follows: 
The dorsal blastoporie lip is formed very little below the 
equator (much less than 25° or 30°, see above) and immediately 
begins to grow over towards the vegetative side. The ventral blasto- 
pore lip is formed about diametrically opposite the animal pole, 
5 © 
Fig. 1. Eight-celled stage seen laterally. Fig. 2. Representation of the situation 
* confine between light and dark area. of the marks a, 6, and c at the time of 
the appearance of the medullary plate and 
of the closing of the blastopore. 
k. Rudiment of the gills. 
1, 2, 3, 4 dorsal blastopore lip during 
the closing. 
* edge of the so-called sense-plate. 
a little bit more to the dorsal side. This border practically does not move‘ 
so that the closing of the blastopore finally takes place at this same 
point. From this ensues that the dorsal blastopore lip progresses through 
a little less than 90° (estimation not under 80°). 
When the blastopore has finally narrowed to a short slit and the 
medullary folds arise, this slit consequently still lies almost diametric- 
ally opposite the animal pole, which is situated exactly in front of 
the cerebral plate. The distance between the two is, when measured 
