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



An effort was made to get an expression for the shape-ratio 

 of the zooids by plotting the^j^ . The plot turned out to be a 

 ragged line showing no semblance of order. 



Taking the individual blocks as shown in figs. 10 and 11, the 

 same general form is seen to hold in all the series measured. 

 The end zooids of Series III and XI-XII were missing, but the 

 other blocks are complete, all zooids being measured up to, but 

 not including the imperfed ones of the terminal remnant. 



In order to compare the different graphs more easily, they 

 were reduced in such a way as to keep the relative curve of each 

 the same as before, but to give them all a common origin and 

 equal horizontal extent. 



This plot is not given, as it brought the eight graphs almost 

 on top of each other throughout their entire length. It is inter- 

 esting to note that the plots differing the most widely from the 

 others were XI-XII and V-VI. It will be seen from figs. 10 

 and 11 that XI-XII is the oldest and largest of the blocks. Its 

 maximum value comes early in the series, the more distal zooids 

 steadily decreasing in size, the last one being smaller than the 

 first one of the block. On the other hand, V-VI starts with the 

 smallest zooid found in any of the blocks and its terminal zooid 

 is much larger than its first one. 



In other words, giving nil tin graphs the .sonic point of origin 

 and the same length, the one having the smallest value at the 

 distal end is the oldest block, the one having the largest is the 

 youngest block. 



Or, biologically speaking, in the youngest block the two or 

 three most distal zooids are larger than the first two or three 

 proximal ones; while in the oldest block, the first two or three 

 zooids are larger than the end ones. The small amount of data 

 under observation is not sufficient to warrant a definite state- 

 ment, but these facts suggest that the distal zooids reach their 

 maximum size first and the more proximal ones gradually catch 

 up. The graphs of the blocks intermediate between the youngest 

 and the oldest tend to confirm this hypothesis, the maximum 

 values appearing nearer the distal end in younger blocks and 

 nearer the proximal end in the older ones. 



