1922] 



MADRAS PEARL FISHERIES 



99 



Date. 



Age. 



Size. 



Average. 



March 18S5 



April i;sS6 



October 1SS7 ... 



November 18SS... 



I ; years 



2§ years 



4f )' ears 



5s y ear s 



March 1889 ... 5| years 



,, 1890 



40 X 64 X 23 millimeters. 



60 X 53 X 22$ 



62 X 58 X 23', ,, 



63X58X27.J 



67 X 64 x 31 



62 X 62 X 30 ,, 



71 X 7° X 32 



79 X 70 X 32 

 8c X 74 X 35 



77 X 80 X 32 

 7S X 7S X 33 



78 x 74 y 



78 X 80 X 33 



80 X 74 X 3 1 



72 X 68 X 31 



-2-2 1 

 33-2 



6* years ...-{ 70 X 73 X 34 

 (_ 76 X 72 X 3U 



J65 X 5^5 X 2275. 



i 



J- 63 5 x 70-5 x 27-5. 



1 

 1 



; ■ 76-66 x 71-33 X 33- 



J 



^76-66 x 77-33x32-83 



J 



] 79 X 77 X 31-33- 



1 



}-72 - 66 X 71 X 32-16. 



J 



March 189 1 ... \ 



I 



Muttuvaratu Par, Ceylon. 



6$ years (deep ") 

 short oysters 

 covered with 



living growth! 

 — Lithotham- 

 nion and 



corals ; much 

 corroded by 

 the tunnelling 

 of C lion a). 



1 73 

 1-67 



So 



63 X 



57 X 



58 X 



6 millimeters 



j 



35h 

 36 



J 



1 

 [•7J-33X 59-33X35*83 



It would appear from the preceding tables that the growth of 

 the Indian oysters is distinctly retarded after the third year, the 

 life conditions being more favourable to the young than to the old 

 — a condition which I believe will be found due largely to the great 

 abundance of encrusting organisms, sponges and polyzoa especially, 

 which begin to flourish upon the valves of the Indian oysters in 

 wonderful abundance from the age of 1% year. A similar 

 state of marked retardation in growth is characteristic of the 

 oysters from the Ceylon South Moderagam Par, after the attain- 

 ment of the same age, a retardation coincident with the appearance 

 of luxuriant sponge, tunicate, and polyzoa growth upon the valves. 

 On the South Cheval where such commensal growth is rare, no 

 such marked slackening in the rate of growth is apparent.* 



The oysters of the Tolayiram Par in October 1887, when 4^3' 

 years old, gave a pearl valuation of but Rs. 3— 1 1—5 per 1,000 and as 



* See my •■ Report on the Biological Results of the Ceylon Pearl Ouster Fishery 

 of 1904" — Ceylon Marine Biological Reports, No. i, Colombo, 1905. 



