PALATJ — BAYER AND HARRY-ROFEN 493 



shadowy shapes of giant blue parrotfishes, perhaps 6 feet long, rise 

 from the depth to which they had fled at our coming, or a shark patrol- 

 ling his accustomed beat, or the faint silvery glint of sunlight on a 

 distant school of swift predators, perhaps some kind of jack (Car- 

 angidae) , near the limit of our vision. 



On the submarine shelf of these undercut shorelines, the coral 

 variety was great, with multicolored Pectinia lactuca, commonly called 

 lettuce coral (pi. 9, fig. 1), green, orange, or brick-red Lobopkyllia, 

 and a few others dominating the shallower areas. The less colorful 

 Plerogyra, with bubblelike tentacles an inch across, the closely re- 

 lated Physogyra, and long, wiry antipatharians (black corals) were 

 usually found on the vertical face of the cliffs. On the shadiest slopes 

 we often met with handsome specimens of Palauphyllia, a subgenus 

 of corals named in honor of their homeland. 



The bright colors of Palauphyllia, like those of most other stony- 

 reef corals, are located not in the coral skeleton but in the soft tissues 

 of the polyps themselves, and are due in part to the presence of minute 

 unicellular algae living in the cells of the endoderm. These remark- 

 able algae, called zooxanthellae, actually serve the coral polyps in the 

 capacity of excretory organs by taking up from the animal tissues such 

 waste products as they can use in their own life processes. They have 

 never been found living free of corals, and have never been artificially 

 cultured. Their only reproductive process seems to be simple division 

 and they are passed on from generation to generation of corals 

 through the eggs, which become infected before leaving the parent. 



Several species of fishes were found only in such situations in Iwa- 

 yama Bay. Among these were the brilliant gold-and-black striped 

 butterflyfish (Chaetodon octofasciatus Bleeker), wrasses of the genus 

 Gheilinus (pi. 10, fig. 2) , and several kinds of cardinal fishes belonging 

 to the genus Apogon. Many species of highly colored fishes that reach 

 a length of no more than one or two inches balance like jeweled 

 spangles among coral branches that rival them in beauty, or conceal 

 their splendor in holes in the coral cliffs. Ever present are the preda- 

 tors that seek out these defenseless inhabitants of the coral slopes. 

 Some, like trumpetfish, have long snouts with which they relentlessly 

 explore all holes and crevices in search of prey; others, such as the 

 turkeyfish, have wide jaws and gaping mouth that enable them to en- 

 gulf their prey in one quick gulp, in much the same way that a 

 vacuum-cleaner may inhale a feather. Solitary sharks were patrolling 

 the bottom of the deep waterways, but their presence was of most 

 importance to the inhabitants of the deeper waters for the sharks sel- 

 dom came to the surface. 



Some of the islands in Iwayama Bay have protected little bay lets 

 in which the coral growth may consist largely of Goniopora, a thick- 



