THE OPALINID CILIATE INFUSORIANS. 



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The genus Cepedea is thus seen to be cosmopolitan, except that it 

 is not known from Australasia or northeastern North America. The 

 absence of Cepedea from northeastern North America, like the ab- 



sence of Protoopalina from the same region, is unexplained. Suit- 

 able hosts are present in abundance. The region is no colder than 

 regions from which both genera are known. The absence of Cepedea 

 from Australia would seem at first thought to be an indication that 



