Invertebrate Gallery of the Indian Museum. 25 



they do not form colonies by budding and fission, but 

 Zoanthus and Epizoanthus are exceptions to this rule, 

 and form encrusting colonies on shells and very often on 

 the anchoring strands of the Glass-rope Sponge. 



The sea-anemones usually live attached to rocks between 

 tide-marks or not far below low-water mark. Some, as 

 Sphenopus. and Cerianthus, which live in deeper water 

 are not fixed, but bury their bodies in the mud of the sea- 

 bottom, leaving the mouth and tentacles exposed. A few, 

 as Polysiphonia, live on the soft mud of the ocean-bottom 

 at the greatest depths. 



Many sea-anemones attach themselves to the carapaces 

 of hermit-crabs or other soft-bodied Crustacea, by whom 

 they are carried about from one feeding-ground to another, 

 the anemone paying for this service by affording the 

 necessary protection to the soft-bodied crab. This inter- 

 change of services between two animals, both of which live 

 in other respects a completely independent life, is known 

 as commensalism. 



When an animal such as a simple sea-anemone gives 

 off buds, or splits itself into two longitudinally to form 

 new " persons," and when these newly-formed "persons" 

 remain attached to the parent and themselves give rise 

 to another generation which also remains attached, and 

 when further the parent and all its attached generations 

 of branching offspring secrete in their outer layer or 

 ectoderm a hard protective coat of carbonate of lime, we 

 then get the common forms of stony-coral. The stone 

 coral, or Madreporarian, is in fact simply a sea-anemone 

 or colony of sea-anemones with a calcified integument. 



ii. ANTHOZOA ACTINIOMORPHA MADREPORARIA. 



The stony corals {Madreporaria) do not all form 

 colonies, but they all secrete in the outer layer of their 



