438 Bulletin American Museum of Natural History. [Vol. XXXV , 



The station has several cemented grades where the heavy collectors 

 are dragged up the sloping beach from the water (Fig. 33). Much of 

 the manipulation is performed under the large thatched shelter shown at 

 the right in the same photograph. 



After a growth of eight or nine months in the protected canal, the pearl 

 oysters are, as stated above, returned to the bay for final growth, or until 

 they are about three years old. 



All pearl oysters placed in the bay for growth are protected in wire- 

 screened crates, and all crates whether containing spawn collectors or grow- 

 ing oysters, are lowered on prepared bottom which has been cleaned of 

 marine growths, and roughly paved with rocks and stones by divers in 

 diving armor. 



The clean stony bottom on which the crates rest, serves also to catch 

 more or less oyster spawn, but the bulk of the set of young shell is secured 

 in the wooden trays of the wire-protected collecting crates. The bottom 

 prepared by the divers is usually in coves, small bays or inlets. 



Each collecting crate when put in proper position, is provided with 

 numerous adult pearl oysters as breeders. Mr. Vives found by experience 

 that some collectors, even when provided with breeders, came up without a 

 good set of young. This he now guards against by putting as many as fifty 

 adults in a crate as spawners, to insure the presence of both male and female 

 oysters, the sexes being separate in the pearl oyster. 



In Fig. 34 some of the matured shell is shown in boxes at the left, 

 while a heap of shell being scraped and cleaned is shown at the right. Figs. 

 35, 36 and 37, show various forms of crates used in collecting and distribut- 

 ing growing shells and protecting them from their enemies. 



There are several hundred spat collecting crates in use, some of them 

 being sent out to favorable points many miles distant from the station at 

 San Gabriel. All crates are protected by heavy, galvanized wire netting 

 of about half-inch mesh. The spawning season of the pearl oyster in this 

 region lasts from October until April or May. The intelligent efforts of Mr. 

 Vives to secure an abundant set of spat in collectors located on the natural 

 beds of the pearl oyster have undoubtedly been successful. 



Two or three crops of matured shell had already been secured when the 

 'Albatross' called at San Gabriel in March, 1911, and subsequently an 

 additional crop of shell was reported for that year. 



Mr. Vives was apparently devoting all his energy to a successful solution 

 of the problems of artificial cultivation and expressed the conviction that 

 his work would prove successful. 



There was abundant evidence that the methods of collecting spat were 

 effective. There appeared to be also an abundance of apparatus for the 

 different operations of pearl shell culture. 



