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TEXTBOOK OF ZOOLOGY 



adaptation to salinity changes to be able to do it. Not only do 

 floods coming" in from streams bring serious disturbances, but the 

 opposite effect may be brought about by storms rolling the waves 



Fig-. 404. — Sacculina. A common parasite on the crab. It is recognized as an 

 arthropod only by its larval stages because the adult looks like a sponge or fungus. 

 A. and B, larval stages with jointed appendages ; C, crab infested with adult Sac- 

 culina. The figure shows it on one .side only. (From Lull, Organic Evolution^ pub- 

 lished by The Macmillan Company.) 



in from the sea. There are opportunity and need for much more 

 study of the effects of these phenomena. 



