S80 PROFESSOR LANKESTER. 



distinguished by being amplii-flagellate, that is provided 

 with both proe- and post-flagellum ; other Monadina are 

 doubly prseflagellate, none are simply post-flagellate. 



Amongst the Schizophytse Professor Cohn has described 

 Spirillum volutans as being amphi-flagellate, wliilst Messrs. 

 Dallinger and Drysdale have made a similar discovery (using 

 it is true the very highest powers of the microscope, and 

 succeeding only with very great care and persistence) with 

 regard to Bacterium termo. 



I am not aware that the simple post-flagellate form has 

 hitherto been recognised as characteristic of any monads, in 

 fact the essential feature of a monad is that it is prseflagel- 

 late. Yet Professor Cohn does not hesitate to leave the 

 forms known as Monas Okenii, M. vinosa, &c. in the genus 

 Monas after he has ascribed to them a single coarse post- 

 flagellum. The possession of this postflagellum and the 

 absence of a prgeflagellum seems to me to necessitate the 

 separation of these forms from the Monadina whilst it is by 

 no means inconsistent with the view that they are form- 

 phases of a Bacterium. 



The flagellum of the locomotive plastids of Bacterium rubes- 

 cens. — Professor Cohn has figured (see the plate accompany- 

 ing the abstract of his paper) postflagella of extraordinary 

 coarseness as attached to the locomotive plastids of B. I'uhes- 

 cens, which he speaks of as Rhabdomonas rosea, Monas vinosa, 

 M. Okenii, and M. Warmingii. He appears not to have been 

 able to see these flagella satisfactorily in all cases, which 

 would be surprising were they as thick as he has represented 

 them to be. I have most carefully examined a variety of 

 locomotive plastids of B. rubescens corresponding to each of 

 Cohn's three monad-species and other varieties which he does 

 not mention. In none of them, not even the largest which 

 attain a length greater than that of Monas lens, which is found 

 with them and has an easily visible prceflagellum, could I get 

 sight of the flagellum, either by long watching in the living 

 state or by the use of reagents such as iodine, magenta and 

 osmic acid. Occasionally I have seen, after treatment with 

 reagents, a coarse filament adherent to one of the locomotive 

 plastids in question, but its presence seemed to me to be 

 accounted for by the fact that small filamentous vibriones 

 and spirilla were abundant in the liquid. At the same time 

 I do not feel ant/ doubt that these locomotive plastids pos- 

 sess one or more postflagella of excessive tenuity. Under 

 a No. 10 immersion of Hartnack, one may follow for half an 

 hour or more the movements of one of these active plastids. 

 I have done this with such a large form as that figured by 



