The Distribution of Senescence 



in old insects, is never far enough advanced to explain their 

 decease (Guthrie, 1953). Cladocera and Amphipoda, together 

 with other small crustaceans, tend to exhibit constant specific 

 age in the laboratory, and may also do so in the wild state. In 

 a natural population of Corophium volutator (Watkin, 1941) the 

 mortality in females rose sharply after maturity. 



Several genera of rotifers also exhibit well-defined specific age 

 in culture (Pearl and Doering, 1923; Pearl and Miner, 1935; 

 Lansing, 1942, 1947a, b, 1948) and almost certainly undergo 

 senescence with significant frequency in the wild state. A 

 population of the tube-building Floscularia marked in the wild 

 with carmine underwent a linear decline, followed by a steep 

 increase in mortality in the final survivors (Edmonson, 1945): 

 the curve obtained in this marking experiment was not far 

 different from those obtained in laboratory populations of 

 rotifers. 



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