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 

 very common. 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 Ccelen- 

 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. Apart from the family of fresh- 

 water sponges (Spongillidae) 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 



