310 SCIENCE PROGRESS 



depths. The advantage drawn from approximately uniform 

 dissemination of the organisms through the pool will be appre- 

 ciated by all who have been in the habit of considering the 

 many natural contrivances which facilitate the spread of birds, 

 insects and common weeds, thereby preventing the waste which 

 would inevitably occur if some areas were regularly congested 

 while others were but scantily populated. 



