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PACIFIC SCIENCE, Vol. XII, July, 1958 
Fig. 1 . Sketch of a major branch system showing branch curvature, positions of branches of different kinds, and 
relative diameters. The largest of the four major branches shown was about 0.5 cm. in length. 
to be produced. The fourth pericentral cell is 
cut off opposite the first and from about the 
fifth segment removed from the apical cell. 
Collections of Cottoniella arcuata made by A. 
J. Bernatowicz in Bermuda (53-380 and 53-96) 
show a similar sequence of pericentral cell 
development. This is in contrast to what 
Boergesen (1930: 146) says is true of his C. 
fusiformis from the Canary Islands. 
The endogenous branches arise (Figs. 5, 7) 
from the anterior ventral surfaces of segments 
in front of or at the corner of the ventral peri- 
central cells. An endogenous branch on a seg- 
ment is somewhat parallel to any exogenous 
branch that may be on the same segment. 
Endogenous vegetative branches develop en- 
tirely like the parent axis and (as in C. arcuata ) 
curve toward the parent axis in their develop- 
ment. The lateral pericentral cells on vegeta- 
tive branches were seen in no case to divide 
other than in the production of exogenous 
branches. In more basal parts of the thalli, the 
longest branches of this sort are up to 675 
microns long. 
