280 



THE EFFECT OF MOISTURE. 



obtained by diluting respectively 950, 900 c. c., etc., 

 of water to a litre; the more saline by concentrat- 

 ing 1050, 1100 c. c., etc., to a litre. The maximum 

 effect on size was produced by a solution containing 

 50 c. c. of fresh water per litre, the increase amount- 

 ing to 15 per cent. With further dilution, the favour- 

 able influence became less and less, till, with water con- 



+ 20J 



415 



>, in 

 Bf-lO 



2 

 PI 



"8 



3 

 a 



850 900 950 1000 1050 



Salinity oi; sea-water 



1100 



1150 



I'M 



FIG. 25. Effect of salinity on size of sea-urchin larvae. 



taining 150 c. c. per litre, it was negative. Thus the 

 optimum salinity is for a much less diluted water than 

 in the case of the tubularians. The present results also 

 differ from these latter in that more concentrated 

 waters have exceedingly little effect on the size of the 

 larvae. 



