68 REPRODUCTION AND LIFE HISTORY. 
But where the ball of cells is practically a solid morula, 
the apparent in-dimpling cannot occur in the fashion de- 
scribed above. Yet in these cases the two-layered gastrula 
Fic. 32.—Life history of a coral, Monoxenia darwiniz, 
—From Haeckel. 
A, B, Ovum. C, Division into two. D, four-cell stage. E, Blas- 
tula. F, Free-swimming blastula with cilia. , Section of 
blastula. H, Beginuing of invagination. I, Section of com- 
pleted gastrula, showing ectoderm, endoderm, and archenteron 
, Free-swimming ciliated gastrula. 
