r.RIEF NOTES ON SPIKOCHiETA ANODONTJE KEYSSELITZ. 387 



Brief Notes on the Structure and Development 

 of Spirocliseta anodontse Keysselitz. 



By 



\%\ Cotil Bo«i.iii<iiiot, :?I.D. 



With Plate 15. 



Much iniceitaiuiy still prevails as to the structure and 

 biological relationships of the spirochfetes. Earlier observers 

 — not altogether influenced perhaps by a desire to prove 

 their affinities with the hasmoflagellates — equipped them with 

 an undulating membrane and a complicated nuclear apparatus, 

 the existence of which is very problematical ; and much con- 

 troversy has existed as to their mode of division, longitudinal 

 or transverse. The very claim of the organisms found in 

 Mollusca, as well as that of the smaller spirochetes, to be 

 called by this name, depending as it must on their relation- 

 ship to Sp. plicatilis Ehrenberg, the type-species, is not 

 very firmly established, since the structitre of the latter — a 

 system of large waves, each broken by smaller undulations 

 superposed on them, with a central axial rod and a series of 

 dots, regarded as nuclei — is markedly different from that of 

 the later additions to the genus. It is desirable, therefore, 

 to record any observations which may tend to throw light 

 on the morphology and life-history of these organisms. 



My own observations have been carried out on Sp. 

 anodonta3, a species easily obtained, and one which may be 

 regarded as fairly typical of the spirochtetes Avhich are 

 parasitic in Mollusca. 



With regard to the so-called undulating membrane of 



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