268 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



As for Saipan, a preliminary survey was made from the incoming air- 

 plane and from maps, and all the likely places noted. On much of the coast 

 line the surf breaks on the main body of land, and the shore drops quickly 

 to a depth of 10 meters or more. This terrain is unfavorable to sponges, espe- 

 cially to any larger than postage-stamp-size incrustations. It is difficult to 

 study because of waves and dangerous because of sharks. Where I did 

 observe such areas with the viewing box, absolutely no sponges could be seen. 

 The likely places were the lagoons within reefs. These were chiefly on the 

 west or lee side of Saipan. 



Using two divers in the water and a viewing box, we spent several hours 

 combing a lagoon area from reef to shore (a few hundred meters) for a 

 long-shore distance of about 4 kilometers without finding a single sponge or 

 even an incrustation as small as a finger nail. Finally, in one area of less than 

 an acre, we found a few score specimens of two species. This area was pecul- 

 iar in that it was sheltered by high cliffs from all directions except the west. 



In Tanapag harbor, with deeper water, several hours search was con- 

 ducted using the usual technique. Two divers were in the water. Large 

 sponges were found; but only about one per acre, and these exclusively of 

 one species (Stylotella agmlnata). This is an outstandingly hardy sponge. 



Saipan has fewer sponges than any area of comparable size and solidity 

 in the world that I know of. 



Guam presented a picture of sponge rarity exceeded only by Saipan. 

 One day I spent several hours wading in shallow lagoon waters using the 

 viewing box and overturning stones and could not find even the most minute 

 trace of a sponge. Later, with the assistance of divers, we finally found nine 

 species, chiefly in a deeper lagoon, between a smaller island and the main 

 land mass (that is, in an area of exceptionally great protection from storm 

 waves). This area covered about 20 acres of water. In the autumn of 1949, 

 only about two months after my field work, a violent typhoon again swept 

 Guam. Mr. A. B. Bronson (who helped me collect), in answer to my in- 

 quiries, said that the area where we found the most sponges was amazingly 

 little disturbed by the hurricane. Flimsy buildings on the shore at that point 

 were undamaged ; trees near there were not mutilated. There are good indica- 

 tions that the topography of hills, shore line, and wave action render that 

 particular locality peculiarly free from storm violence. 



In apparent refutation of my hypothesis as to storm damage, it must be 

 observed that in portions of the West Indies which are subject to violent 

 hurricanes, sponges do thrive. An hypothesis may be advanced to explain 

 this discrepancy. It may be that the West Indian hurricane does ruin many 

 sponges in its immediate path, but subsequently others migrate in from the 

 abundant shallow water areas on each side which are not so devastated. The 

 Marianas are surrounded by great stretches of deep ocean so that their 

 recolonization must be slow and difficult. 



