48 
PACIFIC SCIENCE, Vol. XIV, January I960 
Fig. 3. Geographical distribution of Balanus amphitrite hawaiiensis Broch. 
barnacles grow abundantly in the intertidal zone 
of sheltered coasts, usually below the mean sea 
level; sometimes they occur in clusters on wharf 
piles, coastal rocks, and mangrove roots on the 
leeward side but not on seaward reefs with 
flourishing reef corals. 
In the more northern temperate areas, such 
as the Japanese and Californian coasts, the bar- 
nacles are generally restricted to quiet bays or 
harbors of enclosed water and are usually at- 
tached to floats, buoys, ship bottoms, or sub- 
merged panels under the low tide level. 
They seem to have a tolerance for a wide 
range of salinities (on the average S 16-30 
°/oo), for they are found in the main harbor 
waters where the salinity is that of normal sea 
water but may be subject to at least occasional 
dilution with fresh water. In more estuarine 
situations they are replaced by B. amphitrite 
alhico status Pilsbry or by B. amphitrite kriigeri 
Nilsson-Cantell. On the other hand, in more 
saline waters towards the mouth of bays, B. 
amphitrite communis as well as B. trigonus Dar- 
win dominate in the subtidal zone. A similar 
change in barnacle communities has been noted 
by Day and his collaborators (1956) during 
their ecological survey of South African estuaries. 
From my experience of studies on the fouling 
organisms of naval ships, I am reminded that 
B. amphitrite hawaiiensis was predominant in 
Kure port, on the Seto Inland Sea, but was less 
common in any of the bays facing open seas 
along the Pacific coast of Japan. There the domi- 
nant form was B. amphitrite communis. 
In this connection it is interesting to find a 
similar change of habitats in B. amphitrite den- 
ticulata {— B. a. hawaiiensis) established on the 
Atlantic coasts of France (Bishop et al., 1957). 
According to them, it is always submerged on 
the northern coast but is rare or absent on 
the southwestern coasts of highly estuarine 
condition. 
From these ecological evidences, it seems most 
appropriate to say that B. amphitrite hawaiiensis 
is a protected-water form rather than a poly- 
haline form. B. amphitrite communis, on the 
other hand, is a stenohaline subtidal form; and 
Elminius modestus is a more estuarine intertidal 
form. This last-named barnacle was originally 
found in a temperate habitat, in European wa- 
ters, where it had established itself, so that it 
may extend farther northward than does B. am- 
phitrite hawaiiensis. 
At any rate, marine animals living in an en- 
vironment of variable salinity have their repro- 
ductive cycle of spawning correlated with the 
