232 SPOLIA ZEYLANICA. 



a small growth ratio where they are abundant. That overcrowding 

 is harmful is what one would expect, and the results tabulated in 

 Appendix 4 support this view. If we place the areas in order of rate 

 of increase — ( 1 ) (beginning at the largest rate of increase and finishing 

 with the smallest) and compare this with the areas placed in order 

 with regard to the density of the oysters on the beds (2) (commencing 

 with the areas of low density and finishing with those of high 

 density) — ^we see there is much similarity of order, and that the 

 areas C, R P, L, H, and K support the rule that the more thickly 

 the oysters are disposed the less quickly do they grow. The two 

 statements show as follows : — * 



(1) C, R, J, P, G, L, H, S, M, K, growth-rate. 



(2) C, R, S, M, P, L, H, G, J, K, density. 



With the information now collected it is possible to correct some 

 of the conclusions regarding the age of oysters Avhich were made by 

 Dr. Willey in the earlier stages of the investigation, and in other 

 places to determine the age of the oysters where this was not possible 

 previously. 



In his report of the inspection of March, 1908, Dr. Willey gives 

 a series of measurements, which I will reproduce. To these I have 

 added my computation of the ages of the oysters (placed in italics). 



Table I. — Nachchikkuda. 



May, 1905 (Hornell). — " Very young individuals," size If to 2 

 inches. 



These were about 2 months old. 



June, 1907. — 44 specimens. Average 147 X 159 mm. (5 -88 X 

 6*36 inches). 



These were about 28 months old. 



October, 1907. — 66 specimens. Average 156 X 168 mm. (6*16 

 X 6-72 inches). 



These were about 32 months old. 



March, 1908. — 24 specimens averaged about 162 X 171 mm. 

 (6-48 X 6-84 inches). 



These were about 37 months old. 



Table II. — Kapalturai. 



May, 1905. — The oj^sters had an average size of 2 -92 x 3*33 

 inches. Hornell believed these to be 3 months older than those 

 at Nachchikkuda of the same date. Willey states that "they may 

 be estimated at not less than 1 year old." 



We have every reason to believe that spawning takes place early in the 

 year. Whether there would be a difference of 3 months between the 



* In ( 1 ) the areas which show the highest growth-rate are placed first, and 

 so on, in order of growth rate ; in (2) the areas are arranged so that those with 

 a low density of oysters are placed first. 



