151 
petasus does not carry the fertilized eggs and young 
embryos on its pin nu les, as do the other species of the 
genus Antedon (s.str.) thus far studied as regards their development; 
the eggs drop at once from the pinnules and fali to 
the bottom. The fertilization membrane is covered 
with short spines, almost as a Callionymiis-egg, very different 
from the nearly smooth membrane of the other species. Some- 
times I have seen the eggs floating in the aquaria and would 
suggest that in nature the eggs are really not lying on the bot¬ 
tom, the spinous membrane serving as a floating apparatus. 
The eggs are ca. 0,15 mm, yellowish-red, opaque. The cleavage 
is total and regular. After about 20 hours the embryo begins to 
rotate within the egg membrane, and soon afterwards — generally 
at tne age of about 24 hours — the embryo becomes free, break- 
ing through a hole in the egg membrane 
(Fig. 4). The empty membranes may 
easily be found in the dishes and form 
a very characteristic object. 
The newly hatched embryo is uni¬ 
formly ciliated, only with a tuft of longer 
cilia at the anterior end. In the course of 
the next day the ciliated bands (only 4) 
are differentiated; the yellow cells appear 
in considerable numbers, and the larva, 
seen in diffuse light, forms quite a strik- 
ing object; the said yellow cells are lim- 
ited to the interstices between the bands, 
which appear as broad white lines; only 
very rarely a yellow cell may be seen 
lying in one of the bands. The vestibul- 
ary invagination appears after about 3 days; it is a wide, shallow 
deepening, much as in the other A/tWo/i-species. No suctorial disk 
is formed. At the age of 6 days the formation of the skeleton 
begins. 
It was repeatedly observed that the embryos had considerable 
difficulty in rupturing the egg membrane. I suppose that the lack 
of movement in the water in the dishes containing the developing 
eggs is the main cause of this, and this suggestion is supported 
Fig. 4, An embryo of Antedon 
petasus in the act of leaving the 
egg membrane. 180 /i. 
