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PACIFIC SCIENCE, Vol. IV, July, 1950 
per limits of higher species are fairly definite 
but the lower limits are less pronounced un- 
less there is severe competition. 
There is also the problem of thallus length. 
Thus the long thalli of Pachymenia hang 
down well below the holdfast. Since, how- 
ever, the sporeling phase is probably the most 
critical period in the life history of an alga, 
it is the levels delimited by the holdfasts 
which should be significant. 
If the diagrams (Figs. 9-12) for the vari- 
ous areas are examined it will be seen that 
two major points are emphasized: 
1. The zonation changes with degree and 
manner of wave action. 
2. With increasing exposure to wave ac- 
tion the levels of some species are 
raised, those higher on the shore being 
more affected than those lower down. 0 
At high levels the upper limit of a spe- 
cies is often elevated more than the 
lower. Thus in Figure 13 the lower 
5 The height to which breaking waves raise the 
uppermost tide mark above its predicted or re- 
corded level is referred to as the splash zone. 
limit of Lichina is raised by some 4 feet. 
In areas with maximum wave action 
Lichina and Melaraphe may rise at least 
40 feet higher than normal. 
In other species, e.g., Chamaesipho spp., 
the lower limit may remain unaffected 
whereas the upper limit is raised many feet 
by wave exposure. By contrast, V ermilia and 
Hermella, found in more sheltered areas, are 
apparently independent of wave action. 
In the diagrams it will be noted that Lion 
Rock provides a series of habitats character- 
ized by increasing exposure to wave action 
and depth of water. The diagrams show that 
in the different areas most species retain the 
same relative positions wherever they occur. 
V ermilia and Hermella are exceptions be- 
cause they retain their positions relative to 
the absolute levels. 
Finally, using these diagrams as a basis, an 
attempt was made to summarize the levelling 
data after making an allowance for the in- 
fluence of wave action. The result is depicted 
in Figure 14. Since each species is affected 
differently by wave action, each requires a 
Fig. 10. Vertical distribution of species on the northwest and west of Lion Rock. 
