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



tin- smallest at the ends. The length of the in.ternod.es would be 

 an example of Moll's "Langenperiode der Internodien" while 

 each internode by itself is an illustration of the grand period. 



10. IRREGULARITIES IN THE SERIES. 



A point which may be noted incidentally in connection with 

 the measurements of the series, is that in all the chains one finds 

 now and then a very small zooid in a series of almost uniformly 

 increasing ones. It is often the case that one of the zooids across 

 from it in the other row is correspondingly larger than its 

 neighbors. 



The following are instances taken from series I-II and XIII- 

 XIV: 



