190 



Mr. C. Dobell. 



[Feb. 21, 



I have studied a large number of forms belonging to the Cyanophyceae.* 

 Those which are of special interest in the present case are the spiral forms 

 — Spirulina and Arthrospira. I have made a detailed study of a marine 

 species of the former (S. versicolor Cohn), but have been able to make only 

 fragmentary observations on Arthrospira. I have found that both organisms 

 differ so markedly from all the Spirochaets that I regard the possibility of 

 any close relations between them as excluded. The differences concern 

 especially the cytoplasmic and nuclear structures, and the method of 

 multiplication (in addition to the movements and habits in general). . The 

 similarities observable in the Spirochaets and the spiral forms of Cyanophyceae 

 are merely in respect of certain features common to nearly all the Schizophyta 

 (Bacteria and Cyanophyceae). In agreement with Gomont, I regard 

 Arthrospira as a member of the Oscillatoriaceae : whereas Spirulina occupies 

 an isolated position among the other Cyanophyceae. I have not encountered 

 the remarkable organisms named Glaucospira by Lagerheim, and I am 

 unable to draw any certain conclusions concerning their systematic position 

 from the very unsatisfactory accounts of them which have been published. 



From the standpoint of morphology, therefore, I believe there is no 

 justification for the views that the Spirochaets belong to the Flagellata 

 (or even to the Protozoa), or that they belong to the Cyanophyceae. On the 

 other hand, I think the evidence is conclusive that they cannot be placed in 

 either of these groups. 



If, however, the Spirochaets be compared with the Bacteria,f in respect 

 of the characters enumerated above, it will be found that very striking 

 similarities exist between the two groups. The characters numbered 

 1, 3, 4, 5, 9, 10, 11, 12, 13 are all more or less widely recognised characters 

 of certain of the Bacteria, many of them being characteristic of the group 

 as a whole. Concerning the remaining Spirochaet characters I may add : — 



(a) With regard to (2), I have been able to show that many parasitic and free- 

 living bacillar forms of bacteria and at least one spirillar form (Paraspirillum) 

 are flexible. 



(b) With regard to (7), I have been able to show that a chambered 

 structure of the protoplasm occurs in certain spirillar and bacillar forms of 

 bacteria, both parasitic and free living. 



(c) With regard to (8), I have found in certain Spirilla that there is an 



* My researches on the cytology of the Cyanophycese have not yet been published, as 

 they are not yet finished. 



t My earlier studies on the Bacteria have already been partly published. See 

 especially my " Contributions to the Cytology of the Bacteria," ' Quart. J ourn. Micro. 

 Sci.,' 1911, vol. 56. 



