FISHES ENTRAPPED 233 



the plant had been displaced by the action of the 

 wind, he always found it growing on the shadiest 

 side of a pond, and almost invariably hidden by 

 other aquatic vegetation. From this he inferred 

 that excess of light was prejudicial to the plant, and 

 he remarked that if when kept in an aquarium it is 

 exposed to the full glare of the daylight the valves 

 seemed to lose their elasticity, and the vesicles be- 

 come detached from the stem and drop off. 



A knowledge of these facts may be useful to 

 pisciculturists, who perhaps may not hitherto have 

 suspected so curious a cause of mortality amongst 

 young fry. 



