198 BULLETIN OF THE BUREAU OF FISHERIES 



deal with "Growths on Marine Vessels." The former (1923) is an ecological study 

 based on the examination of 48 vessels, while the second (1924) is a preliminary 

 study of seasonal distribution of the organisms that cause fouling of ships, made 

 while on board a vessel cruising from Hamburg to the West Indies and Central 

 America. 



METHODS 



In order to determine adequately the nature and extent of fouling of ships on 

 the Atlantic coast, it was arranged that the author be notified of the proposed dry 

 docking of all the larger naval craft at several of the United States navy yards, and 

 also by the United States Shipping Board regarding many of their vessels. This 

 enabled the author or an assistant to be present at the time of docking of more 

 than 250 vessels. Notations were made in each case of the relative amount of 

 fouling and its distribution on the various parts of the hxill. Collections of repre- 

 sentative samples were made, which were preserved and carefuUy examined later in 

 the laboratory. Since the material was frequently in a very poor condition when 

 collected, due, usually, to pollution of the harbor waters and to consequent death 

 and partial decay of the growths, exact determinations were not always possible, 

 especially with hydroids, where one often found only empty "stems." For deter- 

 mination of the total amount of folding present, known areas were scraped carefully 

 and the material collected, measured, and weighed while wet; and in some cases 

 the relative amounts of each of the fouUng agencies were determined. In addition, 

 the itinerary of each vessel was secured whenever possible, and the date of previous 

 docking also was obtained. For the great majority of vessels examined the paint 

 used was the "United States Navy standard" (used by the Shipping Board as well 

 as the Navy), and notation was made of all exceptions. On the data thus obtained 

 the following report is based. 



However, in order to determine more accurately the validity of some of the 

 theories that presented themselves during the course of this investigation, consider- 

 able experimental work was carried on simultaneously, and the results of these 

 experiments also are included in their appropriate places. 



NATURE OF FOULING 



As previously stated, the fouling of ships' bottoms is caused by growths of both 

 plants and animals. Among the workers at the dry docks one hears the terms 

 "grass," "moss," and "corals" as describing the types of growths found on ships. 

 It is quite evident that the term "grass " is commonly applied to the stems, or coeno- 

 sarcs, of hydi'oids, and that the term "moss" is applied to the various seaweeds, 

 usually green algae, which are found so commonly near the water line. The term 

 "shells" includes aU shelly growths, such as barnacles, oysters, clams, mussels, and 

 even certain Bryozoa; but more commonly barnacles are recognized as distinct from 

 the other "shells," while the corals so frequently mentioned are probably Byrozoa, 

 for coral itself has been found rarely. 



These groups of organisms, then — barnacles, algse, hydroids, muUusks, Bryozoa, 

 and tunicates — make up the preponderance of the growths that are found on the 

 bottoms of ships. In the determination of the forms collected it has often been quite 

 impossible to ascertain the exact species with finaUty, This was due to the fact that. 



