C@LENTERATA. 109 
or stomachal sac, and consequently internally. But in both there is 
a free communication between these two cavities—a communication 
obvious in the Hydrozoa, and which may be often verified in the 
case of the sea anemones, by the young anemones making their ap- 
pearance at the mouth of the parent anemone, having first escaped 
from the general cavity out into the alimentary cavity of its body. 
The Hydrozoa contains no less than seven orders, which will be 
referred to in our next chapter (VI). The Actinozoa contain three 
recent orders: the Zoantharia (Chapter VII), the Alcyonaria, and 
the Ctenophora (Chapter VIII). 
