1912.] The Life-history of Cladothrix clichotoma (Cohn). 351 



The Formation of Spiral Threads. — Since the announcement of Zopf m 

 1882 of the fact that under certain circumstances Cladothrix dichotomy 

 liberates spiral threads which behave like Spirilla, criticism on this point 

 has been hostile. Winogradsky (20) was strongly of opinion that the life-cycle- 

 of Cladothrix dichotoma was completed by the development of " swarming red 

 cells " which reproduced the threads. He professed himself very sceptical 

 as to the formation of spiral reproductive cells, though pointing out that 

 wavy threads were not uncommon in this species, which every investigator 

 of this species has of course observed. 



Following Winogradsky, the opinion of all subsequent researchers on this 

 subject has set in the same direction. Biisgen (2) accounts for Zopf's 

 Spirillum threads by supposing that a Spirillum, species was present as an 

 impurity, and this in spite of the fact that Zopf had mentioned (p. 10 of his- 

 ' Zur Morphologie der Spaltpflanzen') that he had actually observed these 

 spiral fragments being detached from the thread. Hoeflich(12) takes up the 

 same attitude and denies the existence of spiral threads. The consequence 

 has been that modern writers of text-books on this subject have omitted all 

 mention of these Spirilla. Being convinced of the truth of Zopf's observa- 

 tions on this point I have examined hundreds of samples of Cladothrix 

 cultures extending over a period of 18 months, in order to be able to confirm 

 his observations. 



How the conditions arose I cannot say, but in one culture, and one only 

 I observed the whole procedure as outlined by Zopf. This was in a seven- 

 day-old culture in an open beaker. The medium consisted of a solution of 

 ferrous carbonate to which a drop of 0-05-per-cent. peptone had been added. 

 Between the 7th and the 10th day, the organism fell to pieces. The culture 

 was impure, it is true, but Cladothrix threads are unmistakeable after a very 

 little experience. On the 7th day I found the tufts of threads in a state of 

 violent trembling. The surrounding water contained spiral threads that in 

 the unstained condition could not be distinguished from typical Spirilla. 

 Cilia preparations showed these to possess polar ciliation. Each was seen to 

 be a Cladothrix thread of three to five cells, and with polar cilia. The 

 trembling of the tuft of threads was obviously due to the violent wriggling 

 of these spiral forms in their efforts to free themselves from the colony. 

 Examples of these are given in figs. 20 to 24. Each Spirillum had 1 to 3 

 polar cilia. The Spirillum consisted of from half to three wave-lengths. 

 Some consisted of one cell only. The cilia preparations showed spiral frag- 

 ments in all stages of liberation. In fig. 25 is shown one that has been newly 

 liberated. It was not possible to ascertain whether these Spirilla per- 

 manently retained the spiral form or whether they settled on some object 



