MARINE BIOLOGICAL STATION AT PORT ERIN. 71 



by Dr. Stolterfoth, will be found in the volumes of 

 " Fauna of Liverpool Bay," published by the L.M.B.C. 

 The rest of the marine plants, or sea-weeds, have been 

 reported on by Professor Harvey Gibson. 



PORIFERA. 

 (Fig. II.) 



We all know the bath sponge, but some people do not 

 realise that it is only the horny skeleton of an animal, 

 and that there are many sponges living in our own seas, 

 some of which also form horny skeletons, but which would 

 not be suitable for domestic use because of their contain- 

 ing numerous sharp-pointed glassy spicules or bristles 

 which strengthen and protect the body wall. 



If we omit the minute and very simple unicellular 

 Protozoa, sponges are the lowest of animals. They are the 

 lowest of the " Metazoa," or animals whose bodies are 

 built up of more than one cell. All animals from sponges 

 upwards to the highest are Metazoa, so the primary classi- 

 fication of the Animal Kingdom is into — (1) Protozoa, the 

 first, lowest and simplest animals, and (2) Metazoa, all the 

 rest. Wherever there are rocks and sea-weeds you can 

 find sponges at low tide. For the most part they are 

 found on the lower surface' of stones, or in crevices of 

 rocks, or sticking on the roots of large sea-weeds. Fig. 

 II. shows 3 very common kinds of British sponges which 

 are found almost everywhere round our coasts. Sycon 

 ciliatum (1) and Sycon (or Grantia) comjjressum (2) like 

 many others, have microscopic spicules made of hard chalk 

 or carbonate of lime, while in most of our sponges, as in 



