26 



these months. As a consequence I was led to look elsewhere 

 for some other factor capable of imparting an adequate stimulus 

 to the nerve centres controlling the emission of the reproduc- 

 tive products, and, as already stated, at the end of my inspec- 

 tion of the oyster-beds at Pulicat I arrived at the conclusion 

 that the chief determining stimulus has little or nothing to do 

 with variation in temperature in the case of Southern India, 

 whatever it may have in the north, as for example on the 

 oyster-beds in the neighbourhood of Karachi ; rather did it 

 seem to me a question affected by differences in the density or 

 specific gravity of the water bathing the beds. It appeared 

 to me that so far as the oyster-beds on the East Coast are 

 concerned the spawning maximum synchronizes with the 

 earlier portion of the heavy rainfall period of the north-east 

 monsoon which begins normally about 15th October and lasts 

 through November. At Madras, where the meteorological 

 conditions coincide closely with those prevailing over the chief 

 backwater on the East Coast, the average over 80 years * 

 shows that the total annual rainfall is distributed as follows : — 



4. To test the accuracy of this theoretical deduction, I 

 arranged last September, before leaving on an extended tour 

 on the West Coast, for the conduct of an experiment with spat- 

 collectors in the Ennore backwater to extend through the 

 rainy season of October and November. The material selected 

 consisted of ordinary curved ''• country " roofing tiles. These 

 were given a preliminary coating of lime (ordinary slaked lime 

 stirred into a bucket of sea-water to a creamy consistence) and 

 then in some cases given a second coatiDg of 1 of lime to 3 of 

 sand. The tiles were made into small bundles of six rows of two 

 tiles each, the alternate rows at right angles to those above and 

 beneath, and with the concave surface downwards in all cases. 



V'tdi Russell in " History of the Buckingham Canal Project," Madras, 1898. 



