CHAPTEK III. 

 SPONGES, ZOOPHYTES, AND SEA-FIRS. 



General characters of Sponges Some common Sponges Characters 

 of the Coelentera How to keep them alive General account of 

 Zoophytes and Sea-Firs The common Zoophytes and their 

 swimming-bells The families of Sea-firs Some common Sea-firs 

 Comparison between British Hydrozoa and those of other seas 

 Characters of swimming-bells. 



OF the many-celled animals of the shore the Sponges are 

 the simplest in structure, arid therefore should logically 

 come at the beginning of an account of shore animals. 

 They are, however, far from easy to recognise and classify, 

 and in most cases the determination of species requires more 

 skill and patience than can reasonably be supposed to be 

 possessed by anyone but a specialist. A large part of the 

 difficulty lies in the fact that sponges have no conspicuous 

 external appendages, and no obvious organs which can be 

 used in classification. The classification must therefore 

 depend upon minute characters, especially upon the nature 

 of the spicules points which are often difficult to study. 

 We shall in consequence confine ourselves to such an 

 account of British sponges as will enable the student to 

 know a sponge when he sees it, and to be able to name 

 one or two of the commonest forms. 



In the first place it should be understood that sponges 

 are purely sedentary animals, so plant-like in appearance 

 that they were long thought to be plants. As in so many 

 sedentary shore animals, the young are minute and active. 

 They settle down in sheltered places under overhanging rocks, 

 on stones, on the broad fronds of weeds, and not infrequently 

 on living animals, especially Crustacea. From the places 



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