116 THE SPONGES— PHYLUM PORIFERA 



metazoan, certain cells retain their power to form other types of cells, 

 and these can serve in reproduction. Thus, new individuals are 

 produced before the parents grow old and die. 



Scypha is a very primitive animal, with little specialization of cells 

 as compared with the higher metazoan animals. In many respects it 

 is somewhat like a group of Protozoa stacked together with each living 

 its own life, since the cells are not connected with nerves and the bottom 

 half would not know it if the top half were crushed ; yet it shows some 

 specialization in the collar cells, reproductive cells, and others ; and it 

 does function as a unit in many respects. Hence, it is usually classed 

 as a metazoan, but some prefer to set the sponges apart in a separate 

 subkingdom known as the Parazoa. 



Recent work by A. Whitely has shown that the step from one-celled 

 to many-celled animals may be more narrow than we have previously 

 believed. He took a group of protozoans, Stentor coeruleus, cut gashes 

 in them and fitted them together at the cut regions. The animals fused 

 together and became a multicellular unit. Not only did they unite in this 

 fashion, but there actually began to be a specialization of cells. At one 

 end of the mass of cells a head developed with a mouth which took in food 

 for the entire group. When this head was cut off a new head was re- 

 generated. This work shows how multicellular forms might have arisen 

 from one-celled forms of life. 



The Bath Sponge 



There are a number of other genera of sponges, one of which may be 

 found in fresh water ; but, from an economic point of view, the bath 

 sponge is more important than any of the others. If you were to see a 

 bath sponge in its natural live state, you probably would not recognize 

 it ; it would look more like a slimy piece of raw meat than the sponge that 

 you are accustomed to use in your bathroom or for washing your car. 

 It is only after the living sponge has been taken out of the water and 

 hung up in the air where the protoplasm dies and oozes out of the skele- 

 ton, and this skeleton is washed and bleached, that it resembles anything 

 like the sponges that you are familiar with. The skeleton of the bath 

 sponge does not have spicules as does scypha, else you would scratch your 

 back as you scrubbed it, but has strong elastic fibers instead that make 

 it tough and serviceable. 



This type of sponge grows abundantly in warm tropical waters, and 

 there is a very extensive sponge fishing industry centered around Tarpon 

 Springs, Florida. Sponge fishermen go out in small boats and pull the 

 sponges up from their attachments in the shallow water by hooks on poles. 



