158 University of California Publications in Zoology. [Vol. 6 



could Dot be taken accurately. For length and width, the zooid 

 can be measured Fairly accurately and the results will be com- 

 parable, as the zooid lies flat in the dish for both measurements, 

 but I have not been able to devise a reliable way for taking the 

 third dimension. The zooids of these preserved chains too are so 

 collapsed that the third measurement would probably not be of 

 much value. Consequently we cannot obtain volume relations of 

 zooids, which would be more valuable than mere length. 



The measurements for the first five blocks were tabulated 

 (table 1), the means computed, and this result was plotted as 

 the length-graph. (Fig. 9 A.) The abcissae for this curve rep- 

 resent the place of the zooid in the series, while the ordinates 

 represent the means of the ten series for each place in the series, 

 so that number one is the mean length of the youngest zooids of 

 all the series, number two is the mean of the next youngest, and 

 so on. The same plan was followed with the graph for the 

 widths. (Fig. 9 B.) 



13 17 21 25 29 il J7 41 45 49 53 57 61 65 69 73 77 81 65 



Figure 10. 



