1910 J Johnson: Quantitative Study of Salpa Chain. 



159 



The fact that the blocks arc of different lengths renders the 



taking of the means at each poinl in the scries of less value than 

 if all were the same or nearly the same length, so a comparison 

 was made between the graphs of the different individual blocks. 

 The mean of the two scries of each block was taken fur the graph 

 of the block, giving eight graphs. (Figs. 10 and 11.) These 

 series varied in number of zooids from 55 to 80 and the average 

 size of the zooids differed greatly, as will be seen from the table, 

 since vertical distances represent units of length. 



The graph shown in fig. 9 presents a rapid increase in the 

 zooids at first, the increment gradually decreasing as one goes 

 out until the maximum is reached with the forty-fifth zooid. after 

 which there is first a gradual and then a more rapid decrease. 



A plot was made of the products of the corresponding lengths 

 and widths. This gives a graph of the approximate areas of the 

 zooids. and is necessarily a curve of the same character as the 

 length and width curves with its maximum value near the end 

 of the plot. 



Figure 11. 



