224 ORDER RHIZO-FLA CELL A TA . 



GENUS III. RHIZOMONAS, S. K. 



(Greek, rhiza, root; monas.) 



Animalcules monadiform, adherent to submerged objects by root-like 

 pseudopodic extensions of the posterior region ; the anterior extremity 

 bearing a single lash-like flagellum. 



Rhizomonas verrucosa, S. K. PL. I. FIGS. 26 AND 27. 



Body subspheroidal, its general surface bearing throughout even sized, 

 conical pseudopodic elevations whose length nearly equals one-half the 

 diameter of the body ; similar but somewhat longer conical pseudopodia 

 produced from the posterior extremity, and rooting the animalcule to the 

 selected point of attachment ; flagellum slender, its length equalling twice 

 the diameter of the body ; contractile vesicle single, subspherical ; endo- 

 plast not observed. Diameter 1-1500". 



HAB. Hay infusions. 



This remarkable form was obtained by the author from the hay infusion that 

 yielded Reptomonas caudata. In its normal and fixed condition the vibrations of 

 the flagellum are so rapid and powerful as to maintain the entire body in a state of 

 active tremor after the manner of the wings of many moths when hovering 

 thus rendering it exceedingly difficult to recognize its true form and proportions. 

 This energetic motion becomes, however, even yet more pronounced when, either 

 voluntarily or through a disturbance of the infusion, the animalcule is set free in 

 the surrounding water. Under these circumstances it tumbles over and over or to 

 and fro in apparently the most aimless and excited manner, allowing but an occa- 

 sional and momentary distinct glimpse of either its body or flagellum. In very 

 many instances it was observed that the attached animalcules, either singly or in 

 associated groups of three or four, were immersed within a granular mucilaginous 

 sheath apparently exuded from their own bodies, and out of which the long, powerful 

 flagella alone projected. Such a solitary en sheathed zooid is delineated at PI. I. 

 Fig. 26. 



GENUS IV. PODOSTOMA, Claparede & Lachmann. 



Animalcules amceba-like, changeable in form, emitting pseudopodic 

 prolongations, the free extremities of which are capable of further extension 

 into long, thread-like, and actively motile flagella. 



The single species upon which this genus is founded represents the most perfect 

 known gradational form between the two classes of the Rhizopoda and Infusoria- 

 Flagellata. Unlike Mastigamceba, to which the second place in this category may 

 be allotted, the lash-like organ or flagellum is constant neither in its presence 

 or position, but shares with the pseudopodia the capacity of being emitted from or 

 withdrawn into the substance of the body at any point of the periphery ; two or 

 more of these organs may, moreover, be simultaneously extended from a single 

 animalcule, while in Mastigamceba the flagellum is single and persistent as regards 

 both its position and existence. 



