Vol. XLVIL September, 1924. No. j. 



BIOLOGICAL BULLETIN 



THE GROWTH OF MARINE ANIMALS ON SUB- 

 MERGED METALS. 



G. H. PARKER, 

 ZOOLOGICAL LABORATORY, HARVARD UNIVERSITY. 



In the course of some experiments on the fouling of the bottoms 

 of metal ships, it became apparent that there is a great difference 

 in the ease with which marine animals grow on various metals. 

 To determine the character of this growth, metal plates were sus- 

 pended for the summer months in a floating wooden frame in the 

 Eel Pond at Woods Hole, Mass. The Eel Pond is a shallow body 

 of salt water almost land-locked, but with a strong tidal circulation 

 and with an abundant marine fauna. The plates were set out early 

 in July and were taken in at the end of August or early in Septem- 

 ber. In the first year a number of common metals were tested as 

 well as metals covered with various paints. In the second year, 

 beside metals and paints, a number of metal couples were tried 

 In the third and final year only metals and metal couples were 

 used. The present paper has to do merely with metals and metal 

 couples. The work was done at the Marine Biological Laboratory, 

 at Woods Hole, Mass., to the director, Dr. F. R. Lillie, and the 

 officers of which I am under obligations for many courtesies. 



The metals used in these tests were the common commercial 

 metals aluminum, zinc, iron, tin, lead, and copper. They were 

 suspended in a wooden frame so as to be in solid contact with noth- 

 ing but wood, no metal touching them. Each plate was square, 

 measuring about 15 cm. on a side, and was composed of either one 

 metal or a pair of metals doubly overlapped and hammered to- 

 gether, thus making a seam through the middle of the plate. The 

 plates were suspended vertically so that their upper edges were 

 about 20 cm. under water. 



Animals soon appeared on many of the plates and in some in- 

 stances grew with great luxuriance. In no case, however, was the 

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