THE SPONGES— PHYLUM PORIFERA 117 



In deeper water they go down in diving suits and gather them. The 

 sponges are then hung up to rot and dry, later to be cleaned and bleached 

 for market. When sponge fishing is carried on too extensively in a region, 

 however, there is likely to be a scarcity, and it may be necessary to raise 

 them as a crop just as a farmer would raise corn. Small pieces of living 

 sponge are used as "seed" and are anchored to some solid attachment 

 which is then sunk in shallow water and regeneration takes care of the 

 rest. Within about three years of average growth a sponge will enlarge 

 from one to six inches in diameter and will be ready for market. 



The fisherman, while harvesting them, leaves a little piece remaining as 

 he cuts them from their attachments and so has a perpetual crop once he 

 gets them started. 



Classification and Derivation of Words 



Phylum Porifera (L. porus, pore; jerre, to bear; refers to the small pores 

 which the sponge bears on its body). 

 Genus 1. Scypha (Gr. skyphos, cup; refers to body shape). 



REVIEW QUESTIONS 



1. What is the function of the collar on the collar cells of scypha? 



2. Distinguish between egestion and excretion. 



3. Is the osculum of scypha comparable to the mouth of more advanced forms 

 of animal life? Explain. 



4. Why is the egg always larger than the sperm ? 



5. What is an hermaphroditic animal? 



6. What seems to determine the degree of regeneration possible in an animal? 

 Explain. 



7. Contrast the metazoa with the protozoa and tell why it is difficult to fit 

 the sponges into either group. 



8. How does the bath sponge differ from scypha to make it commercially 

 valuable? 



9. What is the function of the spicules? 



10. Describe the process of budding in the sponges. 



11. Of what advantage to the sponge is a motile larva? 



12. Old age and a natural death were unknown until specialization of cells took 

 place in the metazoa. Explain. 



