230 University of California Publications in Zoology, [Vol. g 



groups: those in which the arrangement is predominantly 

 uniserial, and those in which it is biserial. In species of the 

 uniserial type, the branches consist of internodes which typically 

 possess a single zooecium, this hearing a branch on each side, 

 giving to the colony the appearance of being composed of trian- 

 gular masses of zocecia (pi. 18, fig. 2). While this arrangement 

 of zon?eia is predominant in the uniserial type found here, there 

 is more or less variation, especially in the younger portions of 

 the colony. Internodes sometimes occur which contain four or 

 five zooecia which assume a more or less alternate arrangement. 

 Moreover, the ocecial internode always consists of at least three 

 members, the position of the ooecium being definite and constant. 

 In Crisias of the biserial type, the arrangement of the zooecia 

 is extremely regular, and the general appearance of branches and 

 internodes is so similar that it is impossible to identify species 

 upon either zoarial, or zooecial characters alone, as has been 

 commonly attempted by many of the older writers. Here as 

 throughout the Cyclostomata, oacial characters are of most 

 importance, i.e., position and shape of ovicell, and especially of 

 its aperture. In addition, other characters have been studied 

 and are considered useful. As Harmer ('91) has suggested, the 

 number of zoo?eia in an internode together with the character 

 of the branching are worth considering and are frequently useful 

 for diagnostic purposes. In our species the nature of the branch- 

 ing in the ocecial internode has been found especially charac- 

 teristic, and is offered as another useful character of perhaps 

 greater importance than the method of branching as a whole. It 

 is found that in four species, three, and sometimes four branches 

 occur on the ocecial internode ; also, that a definite relation exists 

 between the position of the ovicell in the internode and the 

 positions of the branches in the same internode. For example, if 

 the ovicell is the third member of an internode (pi. 20, fig. 20, 

 oe.) the first branch will either be absent, as is commonly the 

 case, or arises on the first zooecium: the second branch will then 

 appear on the fourth zocecium (br. 2), and the third on the 

 seventh zooecium (br. 3). If the ovicell is the fifth member 

 (pi. 19, fig. 12), then the first branch (br. 1) will occur 

 on the third Z003cium; the second branch (br. 2) on the sixth 



