SEA-ANEMONES AND CORAL POLYPS. 21 
er portion extends a mass of tentacles of the richest blue, 
and, from their armament of lasso-cells, of the most dan- 
gerous character. They are called Zodids, and are of 
four kinds. Some aid in locomotion, some are reproduc- 
tive, while others are feeders for the entire colony. The 
tentacles are dragged from twenty to one hundred feet or 
more behind. The beautiful filaments form tempting baits 
when lowered, and in this way the Physalia feeds. The 
man-o’-war generally has several tenders, little fishes of 
the family Scombride, of the exact color of the death- 
dealing tentacles, that live under and among them, a won- 
derful case of mimicry.* 
Allied to the Physalia are the Porfita’ and Velella. 
The latter also floats upon the surface, a raft bearing a 
silvery sail, while beneath is the same rich coloring of the 
Physalia. 
Works on Hydroids for further reference. 
“ Acalephs (Jelly-Fishes) of North America, with Pictures of most 
of the Species in Catalogue of Museum of Comparative Zodlogy,” by 
A. Agassiz; L. Agassiz, ‘Contributions to the Natural History of the 
United States,” vol. iv; ‘‘Sea-side Studies in Natural History,” 
Agassiz; “Sertularian Zodphytes of the Coast. of England,” T. 
Hincks; ‘‘ Popular Science Review,” 1878, p. 223; Huxley’s ‘‘ Man- 
ual of Invertebrates” ; ‘‘ Challenger Reports.” 
Class II.—SEA-ANEMONES AND CORAL POLYPS 
(Actinozoa). 
Order I. Actinaria.— These are well represented 
by the sea-anemone, or Actinia (Fig. 20). In appearance 
* The author once swam over the tentacles of a Physalia with an 
almost fatal result; the blue marks were plainly visible six or eight 
months after. These fishes not only mimic the color of the tentacles, 
but assume vertical positions, so that they seem actually a part of 
them. I have often lifted the man-o’-war, which can be safely done 
by the “sail,” and the fishes that were previously unnoticed would 
dart about in the greatest alarm, A more remarkable case of protective 
mimicry is not known. 
