218 SPOLIA ZEYLANTOA. 



larvae from Tutieoriii may l)ocaiTied over to tlie Ceylon peai-1 bank 

 in six days. 



If the monsoon be weak the larvae are carried up northwards , and 

 may even pass through the Paumben Channel. 



According to Southwell and Kerkham, then, if the spawning 

 period synchronizes with a strong south-west monsoon, a spatfall 

 may take place on the Ceylon'pearl banks. 



But there is another point of equal interest which Southwell and 

 Kerkham do not appear to have reahzed. This is dependent upon 

 Homell's statement that there are two spawning maxima in the 

 year, namely, June to August and December to February.* 



If the current work done by Southwell and Kerkham may be 

 relied upon, and if there are two spawning maxima, it follows that 

 not only may the Ceylon pearl banks be repleted in the manner 

 described above, but the Tuticorin banks in their turn receive 

 exotic spat from the Ceylon banks during the spawning period at the 

 end of the year. One has only to look at Kerkham's and Southwell's 

 chart Cf in order to see that if the oysters on the Ceylon pearl banks 

 spawn in December the pelagic larvae may be carried over to Tuticorin. 

 In other words, we have a reciprocal arrangement of the highest 

 importance between the two pearl banks. 



If Southwell and Kerkham had only realized the possibility of a 

 December spanning maximum, they would not have penned the 

 following : — 



■' It follows from the nature of the currents that the Tuticorin 

 banks receive no exotic spat, for as far as we are aware no oyster 

 beds exist around Cape Comorin. Moreover, their own resources 

 are being continually drained, and it is not to be wondered at that 

 they are unprofitable." 



It is true that if there were onh^ the Jnly spawning maximum any 

 exotic spat deposited in the Tuticorin beds must needs have come 

 from some place around Cape Comorin, but the presence of another 

 spawning season in December renders it i^ossible for Ceylon spat to 

 be deposited on the Tuticorin beds. 



The continual drainage of the resources of the Tuticorin beds 

 referred to by Southwell and Kerkham would soon render the beds 

 barren if no exotic spat were received. These fresh supplies 

 probably come from the Ceylon bed, and we must seek another 

 reason for the comparative failure of the Tuticorin beds as a 

 pearling centre. 



The information which may be obtained from the current investi- 

 gations cannot be fully utilized so long as our knowledge of the 

 life-history and spawning habits of the pearl oyster is so imperfect, 

 and it is therefore imperative that these problems should be attacked 



* Southwell only recognizes the first of these. 



I Ceylon Marine Biological Reports Part VI.., 1911. 



