58 ANNALES DE LINSÏITUT PASTEUR 



for several hours 1 was not successfiil in observing- any évi- 

 dence of progressive growth or development in thèse motile 

 forms nor their final séparation from the granule clump as free 

 spirochaetes. I was inclined to attribute this lo the fact that 

 the conditions of the experiment did not sut'ficiently closely 

 reproduce those of the body of the tick; this is the more pro- 

 bable since even the fully fornied long spirochaetes lost their 

 motility in a few hours. Most likely the principal inhibiting 

 agency was the strong light to which they were exposée) during 

 the hours of continuons examination. 



Thèse forms cannot, I think, be explained on the alternative 

 assumption that they represent a rétrograde or degenerative 

 change in pre-formed, adult spirochaetes. Such a view would 

 seeni to be negatived by the facts that, for sonie days before 

 they appeared, spirochaetes had been either absent or extre- 

 mely rare in the other ticks of the same batch and thaï, in the 

 days following the one on which such forms were seen, the 

 tissues of the other ticks of the batch were, once again, seen to 

 be swarming with actively motile spirochaetes. No trace of 

 dead or degenerate spirochaetes was found at the time thèse 

 forms were observed. 



Although the complète observation of Ihe development of 

 young motile spirochaetes from the granule clumps bas not yet 

 been made, I think that the forms 1 bave hère described and 

 figured constitute a strong support of the view put forward in 

 my earlier contributions, namely, that some of thèse clumps 

 represent a stage in a cycle of development of Spirochaela 

 duttoni in the tick. 



Postscript : 1, cannot conclude this Note without saying with 

 what sincère pleasure it lias been contributed to the Volume, 

 as asmall token of the deep respect and admiration which 

 I entertain for M. Metchnikoff and his work. 



Royal Army Médical Collège. London, May 1914. 



