354 



Dr. D. Ellis. 



[May 17. 



latter differs from the former only in having a very delicate and slimy 

 sheath, and in that a common sheath acts as a covering for a large 

 number of threads. Both Fischer and Migula have united Cladothrix and 

 Sphcerotihts into a single genus, to which the name Sphcerotilus has been 

 given. As the mucilage secretion must be largely dependent on external 

 circumstances, it is doubtful, I think, whether it could be demonstrated that 

 the points of difference between the two organisms were other than mere 

 local adaptations. In the only figure of Sphcerotilus natans that I have 

 seen* there was nothing to indicate that the organism was other than 

 Cladothrix dichotoma. The organism described in these pages differs more 

 from the normal Cladothrix in essential points than does Sphcerotilus natans. 

 The conclusion seems justified that we are dealing with what Migula 

 appropriately terms a " Sammel-species." Cladothrix is like Bacillus coli 

 communis, a cluster of sub-species clustered round a central widely dis- 

 tributed form. Migula emphasises this point from a physiological stand- 

 point. The existence of the organism dealt with in these pages and of 

 Sphwrotilus natans demonstrates the fact that from a morphological stand- 

 point also Cladothrix dichotoma must be regarded as a cluster of varieties 

 around a central dominant form. 



Amongst other organisms Crenothrix polyspora and Clonothrix fusca must 

 be regarded as being most closely allied. Their differences are not phylo- 

 genetically of great importance. Slightly further removed are Leptothrix, 

 Gallionella, and Spirophyllum : they differ chiefly in forming reproductive 

 cells by abstriction. At the present state of our knowledge it is unwise to 

 do more than hint at the possible' relationships of Cladothrix with the other 

 members of the higher bacteria. The sulphur bacteria from a phylogenetic 

 standpoint form a highly unnatural group, and Cladothrix is much more 

 closely related to forms like Beggiatoa than this is to the other sulphur 

 bacteria, e.g., Thiophysa or Chromatmm. 



The relation of Cladothrix to Streptothrix, using this term as defined by 

 Cohn and as followed by Eullmann in Lafar's ' Handbuch der technischen 

 Mycologie,' is a very distant one. The whole habit of the latter plant, with 

 its mycelial structure and mycelial mode of branching, shows its relationship 

 with the higher fungi, whilst Cladothrix, on the other hand, is more nearly 

 related to the Algae, and, had it possessed colouring matter, there would have 

 been no difficulty in relegating it to. that class. Among the Algae, the 

 Cyanophyceae is the group to which Cladothrix has the strongest leanings. 

 The general resemblance to forms like Oscillatoria, to Hepalosiphon, and to 

 Plectonema is sufficiently striking to arrest attention. On the other hand, 

 * ' Report of Royal Commission for Disposal of Sewage.' 



