598 SYDNEY J. HICKSON. 
(oosperm nucleus) becomes obscure. The smaller yolk-spherules, which in 
the earlier stages are principally collected round the germinal vesicle, are in 
this stage scattered over the periphery of the distal hemisphere of the ovum. 
The larger yolk-spheres lose their regular spherical shape and appear to be 
breaking up. The trophodise is reduced to a mere nucleated syncytium in 
connection with the canal system. 
Fic. 14.—Young embryo’ of Allopora, showing the first appearance of 
embryonic nuclei after the disappearance of tle germinal vesicle (oosperm 
nucleus). These nuclei are separated from one another by considerable 
intervals, but are all found. within the distal hemisphere. Some of them are 
spherical in shape, some dumb-bell shaped, and a few larger ones are irregu- 
larly ameeboid in shape. 
Fic. 15.—Some examples of the earliest embryonic nuclei yet found. 
Fic. 16.—Stage in the development of Allopora, rather later than that 
represented in Fig. 14. The embryonic nuclei are more numerous, and there 
are no large irregular-shaped ones characteristic of that stage. The proto- 
plasm of the embryo is here considerably vacuolated. 
Fie. 17.—Stage in the development of Allopora, rather later than that 
represented in Fig. 16. The embryonic nuclei are still more numerous and 
scattered throughout the embryonic protoplasm. On the periphery of the 
distal hemisphere there is a thin layer of unvacuolated protoplasm, in which a 
considerable number of the nuclei have ranged themselves. ‘This is the first 
beginning of the ectoderm of the embryo. 
Fic. 18.—A small portion of the periphery of an embryo at the stage 
represented in Fig. 17, more highly magnified. 
Fic. 19.—Some examples of the larger yolk-globules, found in the embryo 
represented in Fig. 17. 
Fie. 20.—Last stage observed in the development of the embryo of Allo- 
pora. Soon afterwards the embryo escapes. The embryonic ectoderm cells 
are now completely formed over the periphery of the distal hemisphere of the 
embryo. On the proximal side the protoplasm of the embryonic ectoderm has 
not yet broken up into cell-masses round the nuclei. 
Fic. 21.—Two stages in the formation of embryonic ectoderm. A. The 
younger stage. B. The older stage. 
Fie. 22.—A small portion of the protoplasm of the inner portion of the 
embryo represented in Fig. 20. 
