50 BULLETIN OF THE 
more evident in the adult, and when new individuals arise distad to any 
two, one of the new ones is median (ancestral branch), the other lateral. 
(So terminal individual of rows 11 and 10; 22, 23; 43, 44; etc.) In 
the diagram, however, I have not always indicated which is the median 
and which the lateral branch, for in the older parts of the colony, owing 
to a shoving of individuals, it is not easy to distinguish them. 
Lateral branches appear usually to be given off towards the axis. 
Here, as in Bugula, the lateral branches tend to be longer; the ances- 
tral, shorter. 
Jt is evident from the diagram that lateral budding is most frequent 
at the margins of the corm, i. e. that part lying posterio-dextral or poste- 
rio-sinistral of the primary individual, and that the descendants of the 
two lateral individuals of the four belonging to generation II. are more 
numerous than those derived from the middle two. Finally, it is evi- 
dent that the number of individuals per unit of are will be the same for 
ares of all radii, and therefore the rate of increase of individuals will 
diminish through successive generations. 
In Orisia eburnea, Linn.,! we find the same laws illustrated. The 
architecture of the genus has been carefully treated of by Smitt (65°, pp. 
115-142) as forming the basis of classification. Barrois (77, pp. 76-85) 
has described in a masterly way the formation of the young stock of 
tubuliporid Cyclostomata, and the relationships of the different types 
of budding in this group. Harmer (91, pp. 145-173) has recently dis- 
cussed the architecture of the stock in British species, adopting Smitt’s 
graphic method of showing it. I have found his paper of great value 
for my purpose. 
This species grows as a shrub-like stock upon floating eel-grass, etc. 
I was wrong in saying, in my Preliminary (’91, p. 282), that Crisia has 
its branches united in pairs. The comparison of this species made by 
Barrois (77, p. 82) with the “geniculata form ” is conclusive evidence, 
to my mind, that the apparent double row is in reality a single one, and 
that such a branch as 18, Figure 65, is to be represented by a single 
line in the diagram Figure 65%. We find here terminal and lateral 
branches ; no true dichotomy. Branches are given off on the side away 
from the axils, as in Lepralia, not as in Bugula. (But branch 11 is an 
exception to the rule.) They are given off, as Harmer C91, p. 131) 
has shown, alternately to the right and left. 
1 This is the only species of Crisia given by Verrill, and, since my species 
is very common, it must be the one to which he refers. Moreover, it agrees 
fairly well with Harmer’s diagnosis (’91, p. 131). 
