444 



PROCEEDIXGS OF THE ACADEMY OF 



Table XXI. 



[July 



The total of 162 in favor of the sediment is quite striking, against the 

 total of 58 eggs without sediment, yet the small number of snails in the 

 experiment must not be overlooked. As the writer did not have a 

 chance to repeat this experiment its value is only suggestive. 



2. Number of Individuals. — In each of seven jars with Ceratophyllum 

 was placed a single snail. In seven other jars similarly arranged were 

 placed two snails each. In ten days the seven snails in seven jars 

 laid 1,149 eggs. The fourteen snails in seven jars laid 1,277 eggs. 



The result of this experiment is similar to the growth experiment. 

 In other words two snails in a jar together do not lay twice as 

 many eggs as a single individual, but each snail lays only half as many 

 eggs as when it is alone in the jar. Thus again is illustrated the bad 

 effect of the presence of the waste products of metabolism in the water. 



3. Effect of Light. — In each of twelve similar jars one snail was 

 placed and Ceratophyllum was added to each jar. Six jars were placed 



Table XXII. 



