OF THE MON.U)INA. 



487 



more slowly in some particular spot, that the two segments must endeavour 

 to tear themselves free, and thus, by twisting in contrary directions, draw our 

 attention to them. It was mthout doubt a specimen of Cryptomonas cylhidrica 

 m this condition which Ehrenberg conceived to be two individuals adhering 

 together and not in the act of fissation. Dujardin failed in seeing spontaneous 

 fission among the Monadina, and thinks it more probable that their multi- 

 plication takes place by the separation of a lobe or of the termination of an 

 expansion, which his notion that they are without any sort of integument 

 presupposes they may, after the manner of Amoehce, push out from their mass. 

 The family is distributed into nine genera, as follows : — 



( Eye wanting 



§ 

 ^ ^ 



( Swimming 



r Single Monas. 



[ Aggregate Uvella. 



Eye present \ ^^^le 



Proboscis one or 

 two 



Proboseides not 1 



I Microglena. 



Chloraster. 



more than four J 



Proboseides j phacelomonas. 



I many J 



^ Aggregate Grlenomorum. 



(^ Rolling Doxococcus. 



Lips present Cliilomonas. 



Tail present Bodo. 



Dujardin was unable to recognize all the genera of Ehrenberg, and believed 

 that Microglena, Phacelomonas, Glenomorum and Doxococcus appertain to 

 another family, and that the distinction between the genera Polytoma and 

 Uvella is erroneously deduced from the supposed fission of Polytoma in two 

 opposite directions and the periodical grouping of Uvella. He thus reduced 

 the genera of Ehrenberg to four in number, viz. Monas, Uvella, Cliilomonas 

 and Bodo, the last comprehending in part his Hexamita, Amphimonas and 

 Cercomonas. The subjoined table represents the distribution he proposed : — 



MONADINA. 



Isolated 



A Single 



FlageUiform « 



Filament. 



Proceeding from the ante- 

 rior extremity. 



/^Moveable in its en- 

 tire length Monas. 



Thickened, and 



moveable only 



I towards the ex- 



\^ tremity Cychdium. 



Proceeding obHquely fi-om behind an anterior 



prolongation Chilomonas. 



^ A second filament or lateral appendage ... 

 A second filament or posterior appendage 



Several 

 Filaments. 



Two equal filaments, terminating the rounded 

 angles of the anterior extremity 



Four equal filaments in front, two tliicker be- 

 hind 



A second filament proceeding from the same 

 point as the flagelliform filament, but thicker, 



trailing and retractile 



^ A filament and vibratile cilia 



. . r Groups always free and whirling 



SB B" I Groups fixed to the extremity of a branching polypidom 



Amphimonaa. 

 Cercomonas. 



Trepomonas. 



Hexaraita. 



Heteromita. 

 Trichomonas 



Uvella. 

 Anthophysa. 



