PALAU — BAYER AND HARRY-ROFEN 497 



fish, not much more than an inch in length, that clings to the stalks 

 of the whip-corals. They may be pursued up one side of the coral 

 and down the other, but rarely will they move to another coral even 

 though it is very near. Our ingenious Rikrik found that by sliding a 

 coral stalk through his fist, he could catch its fish in a small net as it 

 popped off the end. The water was often murky and the light always 

 poor, but we did get a picture of Rikrik catching gobies in a field of 

 junceellas (pi. 16, fig. 1) . Also clinging to the whip-corals were many 

 handsome gray feather-stars, or stalkless crinoids (comatulids) , some 

 of them grasping several corals at once (pi. 16, fig. 2). The cirri (the 

 clawlike "feet") of the crinoids irritated the surface of the corals and 

 scarred it permanently wherever they had clung, indicating that these 

 "free-living" crinoids move about little, if at all. One of the crinoid's 

 distant cousins, a bright orange brittle-star, lived entwined in the arms 

 of the crinoid, and among them could also be found a spider crab, 

 Harrovia, that had joined the partnership. Another crustacean, a 

 small porcellanid crab, scuttled over the surface of the whip-corals, 

 completing this curious association of vertebrates and invertebrates. 



Among the most studied of symbiotic relationships to be found on 

 tropical reefs is that involving several species of large sea-anemones 

 that allow certain kinds of small but colorful damselfishes (genera 

 Amphiprion and Dascyllus) to seek protection among their tentacles. 

 These clownfishes, as they are sometimes called, rarely stray far from 

 their host anemone, and are ready to dart down among the stinging 

 tentacles at the first hint of danger (pi. 14, fig. 2). In spite of years 

 of study, the details of this association are still not clear (Gohar, 1948 ; 

 Gudger, 1946). It is believed that the fishes avoid being stung by 

 swimming in a distinctive fashion that is "recognized" by the coelen- 

 terate. Clownfishes have been seen to drag food to the waiting ten- 

 tacles of the anemones, but, on the other hand, we watched an Amphi- 

 prion seize a tentacle of its host in its mouth and with a few quick 

 tugs pull it loose and eat it. This finny ingrate expected, and received, 

 sanctuary from the very anemone it had been nibbling upon, for it 

 dashed headlong among the tentacles when we approached too closely. 

 Some investigators have suggested that by eating bits of the anemone, 

 Amphiprion builds up an immunity to nematocyst poison, but this 

 suggestion has never been scientifically confirmed. It does seem fairly 

 certain, however, that the clownfishes recognize their preferred species 

 of host anemone partly by sight and partly by chemical emanations. 

 There is also some indication that the anemones do not sting their 

 partner fishes because of some kind of chemical "recognition." 



Coelenterates and echinoderms seem often to play the host role in 

 these partnerships, probably not because of any inherent good nature 

 or native generosity, but because they are slow moving or sedentary 



