29 



Table I. gives particulars of the experiments. 



TABLE I. 



* Experiments 7 to 11. — Water serated by driving air through a piece of punctured rubber tubing, 

 and water supply cut down, one tap supplying tliree tanks. 



In experiment 5, in two of the tanks, a small quantity of sea- 

 weed, chiefly Ulva, came through the pipes when the taps were being 

 cleaned. This was allowed to remain in the tanks, and it was 

 noticed that some of the larvae got under the weed, with the result 

 that they were not so hable to attack from the others when they 

 were moulting. On examination these two tanks contained more 

 larvae than did the other two of the same experiment. Seaweed 

 was therefore used in experiments 7 to 11, and without doubt, by 

 affording shelter, tended to lessen the death rate. 



It will be observed from the talkie that the larvae were kept 

 under observation for periods of about three weeks in each experi- 

 ment, with the exception of experiments 10 and 11. The chief 

 object was to compare the effect of different foods under the same 

 conditions, and space and time did not allow of the experiments 

 being prolonged. In the case of the two last experiments the food 

 was obviously unsuitable. 



