HYDROZOA 131 
tubularian hydroids. These animals are pink in color and move 
through the water with a graceful swaying motion. 
Genus Physalia 
P. arethusa, the Portuguese man-of-war. This colony is perhaps the 
best-known one of the group, since it attracts much attention in Southern 
waters, and is also one of the most remarkable examples of an animal 
community. The most prominent part 
of the compound body is the float, an Aol 
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floats on the surface of the water. Its 
color is bright blue, varying to rose. On _gpW\\uuw 
the upper side of this air-vessel isa crest, or Sj 
sail, and from the under side depend long 
tentacles, or streamers. Some of these ten- 
tacles are covered with stinging- or lasso- 
cells ; some are the feeding zodids, with flask- 
shaped bodies, and some, which look like 
bunches of grapes, are the reproductive 
zovids. The tentacles in this curious cluster 
are all close together and hang from one 
side of the float, near the broader end. The 
longest are on the outside, which may be 
called the windward side, since they serve to 
keep the crest, or sail, before the wind; and 
when the wind is strong they stretch out to 
a remarkable length,— forty to fifty feet,— 
acting as anchors to keep the colony from 
being driven ashore. They also change its 
course by raising the pointed end of the 
float, thus forcing it to “ come about.” These 
long tentacles, ordinarily carried more ordess 
curled up, are in bunches of two to four, and 
emerge from a common stem. Clusters of 
similar, but smaller, tentacles alternate with 
the larger ones, but grow somewhat nearer 
the pointed end of the float ; these are purely 
locomotive organs. Next come two smaller ? S 
sets of appendages, also of unequal size, f 
which are the nutritive organs of the com- &, i 
munity. They are clustered together on a ‘ 
stem like the others. The appendages of Physatiaarethusa, Portuguese man- 
the third kind are small, resemble bunches _°'¥#" 0n¢ ffth natural size. 
of grapes, and are scattered among the nutritive hydra. These last 
are the reproductive zodids of the community. 
oblong pear-shaped bag, full of air, which oo“ 
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Genus Vellela 
V. timbosa. This hydroid is abundant on the Florida coast. It has 
a bright-blue, flattened, oblong, bladder-like float, four to five inches 
