ORDER RA DIO-FLA CELL A TA. 225 



Podostoma filigerum, C. & L. PL. I. FIGS. 28 AND 29. 



Body repent or freely floating, highly polymorphic, almost spherical 

 when contracted, substellate with attenuate pseudopodic prolongations 

 when extended ; the distal terminations of the pseudopodia produced as 

 long, thread-like, vibratile flagella, which are capable of contracting in a 

 spiral manner, or of being entirely withdrawn into the substance of the 

 pseudopodium ; contractile vesicle single, endoplast distinct, subspheroidal. 

 Length of extended body 1-500". 



HAB. Fresh water, among aquatic plants. 



Overlooking the presence of the flagellate appendages, this animalcule, as 

 remarked by Claparede and Lachmann, closely resembles in its stellate condition 

 the Amoeba radiosa of Ehrenberg, while at other times, in its contracted state, it 

 might be as easily mistaken for A. diffluens. Any food-particle arrested by one 

 of the flagellate appendages is immediately withdrawn with the latter into the 

 substance of the pseudopodium that carries it, a slight depression momentarily 

 marking the point of entrance. Biitschli,* while recently proposing to identify 

 Ehrenberg's Atnczba radiosa with this type, has sought to demonstrate that the 

 radiating pseudopodia of the former are capable of similar attenuate prolongation 

 in the form of flagella. An intimate acquaintanceship with the Amoeba named inclines 

 the author, however, to regard the two as distinct, and that Biitschli must have 

 had Claparede and Lachmann's type, and not Ehrenberg's, under examination. In 

 the latter species, however finely attenuate may be the extensions of the pseudo- 

 podia, they never assume the form and functions of vibratile and spirally contractile 

 flagella. This decision is entirely confirmed by an examination of the exhaustive 

 figures and accompanying description of Amoeba radiosa embodied in Professor 

 Leidy's monograph of the North American Rhizopoda, previously quoted. 



Order III. RADIO-FLAGELLATA, S. K. 



Animalcules emitting numerous ray-like pseudopodia, after the manner 

 of the Radiolaria, and provided at the same time with one or more 

 flagellate appendages ; no distinct oral aperture. Mostly marine. 



The several genera referred to this newly instituted Order of the Flagellata 

 form two natural and well-differentiated groups. In the one that of the 

 Euchitonidae we find types which, except for the presence of the characteristic 

 flagellum, are not to be distinguished from the ordinary representatives of that 

 typical Radiolarian group known as the Polycystinae ; while in the second one that 

 of the Actinomonadidae are presented forms that most intimately unite the more 

 typical flagellate monads with the Heliozoan group of the same Radiolarian class. 

 Since it is now demonstrated of all the other leading groups of the Radiolaria 

 so far investigated, that their initial conditions take the form of simply flagellate 

 monadiform zoospores, it may be consistently predicated that in the two above- 

 named family divisions is permanently retained that primitively developed locomotive 

 organ which among the more ordinary Radiolaria becomes aborted at an early 

 epoch of their existence. 



The direct metamorphosis, observed by the author, of a flagelliferous zooid 

 into an adult Radiolarian type of structure, as exemplified in the genus Actinophrys, 

 will be found illustrated at PI. I. Figs. 9-11. As first observed, see Fig. 9, the 

 monadiform germ closely corresponded in appearance with the Peranema g/obitlosa 



* " Beitrage zur Kenntniss der Flagellaten," ' Zeit. Wiss. Zool.,' Bd. xxx., 1878. 



Q 



