PLACUNA FISHERY. 133 



II. — Age of the Oysters. 



I take it that my inspection of the Taniblegam beds in June and 

 October, 1907, allows me to assert positively that there was np 

 effective fall of spat in that year ; and I found no evidence of any 

 having taken place in 1906. In June I did find yearling oysters in 

 the Sambore river, but not in lake Taniblegam.* 



The following tables show the growth of the oysters on the various 

 beds since Mr. Hornell's inspection of 1905. f The term " plants " 

 is applied to those oysters which I placed in an enclosure in Nachchik- 

 kuda in October, 1907, as will be mentioned later. Oysters taken 

 from their natural positions on the beds are distinguished, when 

 necessary, as " topotypes" : — 



Table I. — Na<^hckikkiida. 



The (UnH'n(si<jns given in this and subsequf at tables are the averages 

 of numbers of individuals, the numbers in each case being stated for 

 the sake of completeness, although the actual Jiumber makes no 

 appreciable difference to the. average in a normal series. The standard 

 height is 5 1 inches or 139 mm. In the measurements given below the 

 length precedes the height. 



Date. Observations. 



May, 1905 (Hornell) . . The bed " consists of very young indivi- 



duals, none exceeding the size of a 

 crown piece," i.e., If to 2 inches in 

 diameter, or aljout 50 mm. 



Jmie, 19U7 . . Average of 44 specimens : 159 by 147 



mm., deciinal points being oinitted. 



October, 1907 . . Average of 66 specimens : 168 by 154 mm. 



March, 1908 . . Average of 9 " plants " : 173 by 163 nmi. 



Do. . , Average of 15 topotypes : 171 by 162 mm. 



The averages taken in March of this year show that the transplanted 

 oysters behaved normally. 



TaMe II. — Kapalturai. 



May, 1905 (Hornell) . . ' The bed off Kapalturai is also composed 



of young individuals, older by some 

 three months than those of Naclichik- 

 kuda. The avei'age size is 3*33 inches 

 by 2-92 inches (83-25 by 73 mm.), and 

 over the gi-eater part of the bed they 

 lie in gi'eat profusion, from 10 to 22 

 being commonly brought up at one 

 dive." These may be estimated at not 

 less than one year old. 



June, 1907 .. Average of 16 specimens: 6*6 by 6*1 



inches , or 1 65 by 1 52 mm. These would 

 be tliree years old. 



October, 1907 . . Average of 15 : 169 by 153 mm. This is 



nearly the same as the Jvuie average, 

 and just double the 1905 average ; 

 about 3i years old. 



* A. Willey. Report on the Window-pane Oysters (Jmie, 1907). Spolia 

 Zeylanica. Vol. V., November, 1907, p. 38. 



t J. Hornell. Report on the Placuna placenta Pearl Fishery of lake 

 Tampalakamatn (Ma.A-. 1905). Ceylon Mar. Biol. Lab. Rep., Part II., June, 

 190(i. 



