20 ANNIE PORTER 



is considerably higher than tliat of the iiiterior of either Ano- 

 don or oyster, the Spirochaetes were not killed, and the only 

 effect was that their movements became far more rapid, 

 slowing again when the préparation was allowed to cool. This 

 behaviour is in accord with that of blood inhabiting Spirochae- 

 tes whose movements I hâve seen slacken greatly when they 

 are cooled, thoiigh hère there are factors other than tempéra- 

 ture to be considered, Fantham found that a température 

 of 30° C. was fatal to the Spirochaetes of Lamelhbranchs in a 

 very short time, and that lowering their température prolon- 

 ged their Hfe. 



Effect of the fluidity of the médium. In the case of 

 S. miodontae, I found a certain number of infected styles whose 

 posterior ends were notably softer and more fluid than their 

 anterior ones. The Spirochaetes in the softer, more fluid parts 

 were more active in their movements than those in the denser 

 parts of the style. 



That the Spirochaetes of Lamelhbranchs are capable of endu- 

 ring sudden changes of density of média is obvions. On one 

 occasion, I saw three Spirochaeta anodontae swim through the 

 style of an Anodon into the liquid around the style, then 

 retrace their path and re-enter the style. This style showed 

 a central, more refractile zone, and into this the Spirochaetes 

 swam, remaining quiescent there for some time, but finally 

 returning to the outer zone, where they resumed their active 

 movements. 



When the density of the médium was greatly increased by 

 concentration, the Spirochaetes died. Once the viscidity of the 

 liquid surrounding the parasites was increased by adding gly- 

 cérine. This had the effect of slowing their movements. On 

 other occasions in fresh préparations, when the coverslip had 

 been carefuUy vaselined at the edges, I hâve seen Spirochaetes 

 swim out into the vaseline, and remain there, moving quite 

 normally for many minutes. 



Effect of light. Individuals with bodies coiled on themsel- 



