42 BULLETIN OF THE 



arrangement of the individuals in Figure 64. The radial lines repre- 

 sent the rows of individuals ; the concentric lines separate adjacent 

 individuals of the same radial row. The same nomenclature is used 

 as in Figure 64, 



In studying Figures 64 and 64*, one of the first facts which attracts 

 our attention is that (1) the individuals of the twigs are in pairs, and 

 the adjacent individuals of the two rotvs " break joints." In general, one 

 finds that the individuals of the same twig are of the same length ; but 

 since the two rows of any twig ultimately rest upon one, either the prox- 

 imal two individuals of these rows must be of unequal length, or else 

 they must arise on different parts of the individual which supports 

 them. Both of these cases occur. Sometimes one individual (26 IX.) 

 has nearly twice the length of the other (25 IX.), and in other cases 

 (9, 10 VI., 11, 12 VI.) the more proximal of the two individuals 

 (9, 10 VI.) arises so far proximally on the side of the supporting indi- 

 vidual 9-12 V. as to have a total length quite equal to that of the more 

 distal (11, 12 VI.). Owing to their different positions upon the indi- 

 vidual 9-12 v., tliese two individuals may be designated as lateral 

 (9, 10 VI.) and terminal (11, 22, VI.). The terminal individuals con- 

 tinue the ancestral roiv ; the lateral individuals are the first of lateral 

 branches. 



This distinction is an actual, and by no means a meaningless one. 

 The constant difference in position of the two individuals which rest 

 upon one shows conclusively that this branching cannot be regarded as 

 dichotomous, and I may say parenthetically that I shall try to show 

 in the general part of this paper that true dichotomy is not com- 

 mon in Bryozoan stocks, if indeed it exist at all. Now, since in 

 the rows of individuals in which there is no lateral budding the 

 distal lies directly terminal to the proximal individual, that individual 

 which fulfils this condition at the region of bifurcation of the twig 

 must be regarded as continuing the ancestral branch ; and that 

 individual, conversely, which arises from the side of the single prox- 

 imal individual must be regarded as the lateral one. Thus we have 

 the stock composed of ancestral and lateral branches as represented 

 in Figure 64^ 



(2) When tivo lateral branches are given off from two ancestral ones 

 which have had a common origin (and are consequently themselves re- 

 spectively ancestral and lateral branches), they are given off toivards 

 each other. This is equally true whether the two lateral branches in 

 question arise in the same generation (32 X., 33 X.) or in different 



