ART. 1 ANCYLOSTOMA PLURIDEN^TATUM SCHWARTZ 9 



buccal capsule containing in the anterior ventral portion one pair of 

 well-developed teeth and one pair of small or rudimentary teeth. In 

 certain specimens of A. 'braziliense collected by the writer from a cat 

 which was shipped from Florida the inner pair of small teeth was 

 found to be entirely absent, whereas in other specimens from the same 

 host it was present. This observation suggests the possibility of the 

 occurrence of a variety of Ancylostoma 'braziliense containing but a 

 single pair of teeth. Such variation, if germinal in character and not 

 due merely to external causes, undoubtedly represents an incipient 

 species. It is suggested, purely as an interesting speculation, that the 

 various species of Ancylostoma containing less than three pairs of 

 well-developed teeth in the anterior oral margin may have arisen 

 from forms containing three pairs of teeth, each species representing 

 a mutation. 



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 Darling, Samuel T. 



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1923. — On the parasitic nematoda collected from mammalian hosts which 

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