attachment began in April, reached its yearly maximum in June, 

 decreased markedly during July, and reached a secondary maximum 

 in October. Barnacles did not appear on the panels from December 

 through March. Andrews (1953) gives the peak setting period for 

 one species of barnacle ( Balanus improvisus ) as May and August 

 or September. The presence of the primary and secondary maxima 

 has three possible explanations: 1) two separate spawnings of the 

 original spawning stock occurred; 2) the secondary maximum repre- 

 sents a second generation resulting from the individuals setting in 

 May and June; 3) the two maxima indicate two different species having 

 different breeding seasons. The first setting was composed of Balanus 

 improvisus , and although this species has been identified in the 

 second setting, no other species was positively determined to be 

 present in the second set. 



A possible indication of the competition between individuals for 

 both food and space may be gained by comparing the size curve 

 with the curve representing the number of individuals. During the 

 short time available for individuals to grow (1 month), the average 

 size attained was much greater during the period of minimum attach- 

 ment than during periods of maximum attachment. 



Figure 9B shows plots of number and size of barnacles attaching 

 to panels exposed for progressively longer periods. On these panels 

 barnacles appeared in great numbers during May and June but corre- 

 spondingly fewer were found on panels exposed for progressively 

 longer periods. This rapid decrease in numbers with time probably 

 indicates that the numbers of dead barnacles increase as the numbers 

 of succeeding foulers increase. After the 7th month most observed 

 barnacles were dead. Many others were overrun by bryozoans and 

 colonial hydroids making a count of individuals difficult. Barnacles 

 which were not overrun by other fouling forms continued to increase 

 in size. Size determinations of dead organisms become less reliable 

 with time, however, and the sizes determined for the 10- and 11-month 

 panels may not be representative. 



Plots were made of sizes and numbers of barnacles only on the 

 convex side of panels. However, the trends of numbers and size on the 

 concave side were similar to those on the convex side. 



2. Colonial Hydroids 



The number of colonies and the average length of colonial hydroids 

 are plotted in Figure 10. Figure 10A shows the results obtained from 



11 



