The President's Address. 141 



tional way, though they are so frequent in a species of Paramecium 

 as to have been formerly mistaken for spermatozoa. The relations 

 of bacteria to sponges, to hydroid polyps and sea-anemones, cannot 

 fail to yield valuable results when studied, and those occurring in 

 the gut of Annelids and Molluscs, when the digestive secretions 

 are also studied, must give new insight into the whole subject. 

 In the great Sipuncuhts nudus, common at Naples, I found years 

 ago that the remarkable little csecran placed near the rectum is 

 not unfrequently distended and tilled with a cream-like mass of 

 delicate bacilli. 



Lastly, I would venture to mention to the Society an extremely 

 interesting organism connected with the Bacteria — one of the 

 Cyanophycea; — which exists at our doors in London, namely in the 

 " museum-lake " at Kew Gardens, where it was originally discovered 

 fifty-five years ago by Henfrey, who gave to it the name Clathro- 

 cystis aeruginosa. In masses it has a strong apple-green tint, which 

 on drying turns to a verdigris blue if exposed to sunlight, but not 

 if kept in the dark. It is associated with Amphanizomenon and 

 Anabcena, and there is much to suggest that it is a "glceococcus" 

 phase of one of those genera. It has a special interest for me as 

 resembling some of the peach-red coloured bacterial growths which 

 I described many years ago as Bacterium rubeseens. Professor Ferdi- 

 nand Colin, of Breslau, considered the " glceococcus " phase of that 

 rubescent organism to be referable to Henfrey's genus, and called it 

 Clathrocystis roseo -persicina. T have again this year made some study 

 of Henfrey's C. <-i>ruginosa, especially as to the existence of nucleus 

 or nuclear matter, but I have not now proper opportunity for its in- 

 vestigation. The question of the genetic relation of " glceococcus " 

 forms to the filamentous Bacteria and Cyanophycea is well worth 

 the attention of microscopists. I formulated many years ago the 

 view — based on my study of Bacterium rubeseens — that this is (as 

 also are other but not all Bacteria) a polymorphic species, and that 

 the red Clathrocystis is one of its growth-phases, others being long 

 filaments, very large bacterial forms, remarkable disks, and also rod- 

 like growths and HydrodictyonAike networks. Zopf subsequently 

 advocated the same view and gave illustrations of polymorphic 

 phases, not only from my B. rubeseens (Cohn's C. roseo-persicina), 

 but from other forms, such as Beggiatoa, which serve to connect 

 the Cyanophyceas and the Bacteria. But of late years the view 

 seems to have prevailed that our polymorphic growth-phases are 

 distinct species and genera — a conclusion the truth of which I do 

 not think has been made probable, much less established. I should 

 like to see the whole question re-investigated. 



