GUIDE TO FOULING ORGANISMS 



The visible fouling organisms belong to seven 

 main groups. In spite of the fact that tlie dif- 

 ferent kinds in each group may vary widely in ap- 

 pearance, tbey all have certain features in com- 

 mon, and as these features are easy to recognize, 

 any given organism can be placed in the proper 

 group. 



Three of the groups are characterized by hav- 

 ing hard, often limy shells. These are the An- 

 nelids (worm tubes) , Barnacles, and Molluskso 

 Three other groups (the Algae, Hydroids, and Tu- 

 nicates) include only soft— bodied forms. The 

 members of the remaining group, the Bryozoa, are 

 mostly soft— bodied, but a few have limy shells 

 which form encrusting patches. Thus to identify 

 any sort of fouling organism, the first step is 

 to learn if it has a shell. Next the table on 

 oage 10 should be consulted, and finally the 

 . lent if icat ion obtained from this table should 

 be checked with the description of the group to 

 whicb the organism seems to belong. 



When there is difficulty in classifying a 

 soft— bodied form, placing it in a dish of water 

 will sometimes help to show its characteristic 

 structures. 



The terms grass and noss are popularly used 

 for Bryozoa and Hydroids as well as Algae, but 

 they do not have definite meanings when applied 

 to marine organisms. True grasses and mosses do 

 not occur in the sea. 



8 



