NOTE ON BACTERIUM UUBE.SCENS. 279 



When I look at the feebly-magnified and really unsuc- 

 cessful portraits which Professor Cohn has given of these 

 red-coloured Schizophytes (some of which are copied here for 

 the use of readers), I am less surprised at his maintaining 

 the generic and even ordinal distinction which he assigns to 

 them than I should have been, had his drawings given evi- 

 dence that he had devoted to these forms that care which 

 they deserve. 



In the first place a higher power than 600 diameters 

 should be used, and drawings of the individual cell of every 

 vai'iety of form and structure should be given in illustration 

 of the view that Clathrocystis roseo-persicina is distinct from 

 Monas vinosa and M. Okenii. Instead of this, I must most 

 distinctly point out that Professor Cohn has omitted to figure 

 the intermediate forms which are abundant in most gatherings, 

 and were so in those which I sent to him. In fact, either 

 my figures of such forms in my papers in this journal in 

 1873 and 1876 are inventions, or Professor Cohn has ignored 

 their existence. It must be remembered that Professor Cohn 

 has had the opportunity of examining two samples of these 

 organisms sent by me, in support of the view which I have 

 taken with regard to them. 



Whilst referring the reader to my previous papers — the 

 statements in which I can from new studies made this 

 summer most fully confirm in every particular (excepting as 

 to the movements of the large bacterioid plastids, which I 

 did not discover until after my first paper was published) — I 

 may here draw attention to some inaccuracies in Professor 

 Cohn's descriptions of the Clathrocystis-forms, and the 

 so-called Monas-forms of Bacterium rubescens. 



Use of the generic term Monas. — When we inquire into 

 the characters which both Ehrenberg and Dujardin have 

 assigned to the family Monadina, as indicated by the forms 

 placed there by them, we find that the most essential feature 

 of a " Monad '^ is the possession of a remarkable vibratile 

 cilium, which is extended in front of the organism, and which 

 it follows (as it were) in its movements. This characteristic 

 monad-cilium, which may be called a '' prseflagellum," 

 must be broadly distinguished from a ''postflagellum," such 

 as the tail of a spermatozoon, which drives the " head " 

 before it — the whole mechanism of the movement in the two 

 cases is in contrast, and the two organs (the leading and the 

 driving llagellum) deserve to be distinguished more widely 

 than any two forms of vibratile protoplasm. Euglena and 

 Astasia furnish admirable examples of the prseflagellate form 

 as well as the common Monas kns. The genus Bodo is 



