Natural history and propagation of fresh-water mussels . ringwhich it occurs, and with other conditions which are not fully understood. The resultsof some recent experiments indicate that glochidia of long-term breeders have a rela-tively long infection period when they are infected upon fish shortly after maturingand a relatively short period when infected after they have remained in the marsupialpouches over winter; that is, young glochidia complete metamorphosis in parasitism more slowly than old glo-chidia. The temperature ofthe water seems to be oneof the factors governing theduration of
Natural history and propagation of fresh-water mussels . ringwhich it occurs, and with other conditions which are not fully understood. The resultsof some recent experiments indicate that glochidia of long-term breeders have a rela-tively long infection period when they are infected upon fish shortly after maturingand a relatively short period when infected after they have remained in the marsupialpouches over winter; that is, young glochidia complete metamorphosis in parasitism more slowly than old glo-chidia. The temperature ofthe water seems to be oneof the factors governing theduration of the parasiticperiod, and doubtless thevitality of the host fish isanother; but there is diver-sity even among glochidia of the same species when infected on the same fish. Lefevreand Curtis (1912, p. 168), for example, show under such circumstances variations from9 to 13 days, and even from 13 to 24 days. The following instances (Table 17) fromrecords at the Fairport station are illustrative: Tablb 17.—Infections Showinq Duration of Parasitic Fig. -A dorsal view of a juvenile pink heel-splitter showing glochidial shell stillvisible. (Xi8). Species of mussel. Species of fish. Date ofinfection. Duration ofinfectionin days. Averagewater tem-peratureduringperiod. June 5,1919June 20,1919July 14,1919 1312II1312131310II 13 101212121110 IS 131419 20 68()(«)6to S 9 to II 11 to 1211 14 to 18 14 to 2 1 Do do Do do Do .. do Do do Lampsilis luteola Do Do do Do do Do ....do .... do Do do July do ... Do ... do Do do do Do .... do Aug. 21,1919 Do do Do .. do Aug. 22,1919June 30,1919 do Do do Do do Lampsilis luteola July 2; 1914 Do Do Aug. 16,1914Aug. :;July 13,1918July Do do Do Do Do do 75-576. 578. 3 Lampsilis fallaciosa do ....do QltnHrnlp Jipfft^ n still carrying infection, Apr. 14, 1915. In about one wee
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