THE SCHOOL OF THE SHORE 17 
deeper water there are Alcyonarians, such as 
Dead-Men’s-Fingers, often thrown up in great 
quantities after searching storms. In warmer 
seas the branched Sea-fans or Gorgonians are 
verycommon. Everywhere there are zoophytes 
or hydroid colonies, some of which give off 
swimming-bells or medusoids in the summer 
season. When a Stinging Animal (or Celen- 
terate) becomes very calcareous it is called a 
coral, and so there are corals related to sea- 
anemones (such as reef-building corals and 
cup corals), others related to Alcyonarians 
(such as the precious red coral and the organ- 
pipe coral), others related to hydroids (such 
as the close-grained millepores). 
SPONGES.—A part from the family of fresh- 
water sponges (Spongillide)—doubtless emi- 
grants from the shore—all sponges are either 
shore-animals or deep-sea animals. In other 
words, they are sedentary and require a sub- 
stratum on which to grow. The Crumb-of- 
Bread Sponge (Halichondria panicea) grows 
on the shore-rocks, with exhalant openings 
like the craters of volcanoes; the Purse Sponge 
(Grantia compressa) often has to endure pro- 
longed exposure at low tide; the Bath Sponge 
