GENERAL BIOLOGY 



785 



of plaice, marked them, and let them go again. He then kept 

 account of the percentage of marked plaice subsequently 

 recaptured, and comparing this percentage with the total 

 catch according to the fishery statistics he hoped to arrive 



Fn;, 575.— C. G.J. Petersen's Bottom-Collector. 



approximately at the proportion between the number of plaice 

 caught by the fishermen and those living in definite regions. 

 In restricted areas, where immigration and emigration are 

 insignificant, his interesting experiments have yielded very 

 good results, providing probably the only accurate knowledge 

 at present available regarding the abundance of fishes in the sea. 



J. H. 



3E 



