THE ABALONES OF CALIFORNIA 



547 



some months beautiful pearls were secreted, their size being in propor- 

 tion to the length of time of the culture. 



In our red abalone a boring mollusk, Plioladidea, penetrates the 

 shell from the outside. It files its way, by means of sharp teeth on its 

 shell and possibly by the secretion of sulphuric acid. The burrow 

 enlarges, as the Plioladidea, growing in size, digs its way in. When 

 near the inner pearly layer of the abalone shell, the host resists the 

 oncoming Plioladidea by secreting more nacreous matter. Thus the 

 defensive wall, eaten by the Plioladidea, grows inwardly as a mound- 

 shaped projection, the blister-pearl. In imitation of this natural 

 process, a hole is drilled through the abalone shell and a form is 

 inserted. This form, made of shell, is shaped like a long-shanked collar- 

 button and so placed that the expanded curved base lies against the 

 pearl-secreting mantle. The shank projects from the outer surface of 

 the abalone shell and is there made fast by aluminum wire, to which 

 a metal tag, bearing the serial number, is attached. In some cases the 

 wire has corroded, with the loss of the tag. In later experiments the 

 numbers have been filed upon the shell. The black abalone has been 

 used in most cases, although a few experiments have been made upon 

 the green abalone. Holes have been drilled through various parts of 

 the shell and different numbers of forms inserted. In addition, spher- 

 ical forms, without shanks, have been placed beyond the mantle cavity 

 near the visceral hump. I have succeeded in raising abalone culture 



The Japanese Abalone Camp at White's Point, California. 



