GENUS ACTINOMONAS. 227 



Actinomonas mirabilis, S. K. Pl. I. FiCx. 18. 



Body subspherical or ovate, seated on a slender pedicle, which usually 

 equals two or three times the diameter of the body ; endoplasm trans- 

 parent, slightly granular ; flagellum very long and slender, extended rigidly 

 and arcuately in advance ; pseudopodia equalling in length the diameter 

 of the body, very numerous, radiating from all points of the periphery ; 

 contractile vesicles two in number, situated close to each other in the 

 posterior region of the body ; endoplast spherical, subcentral. Diameter 

 1-2000". 



Hab. — Salt water. 



Several examples of this interesting type were met with at St. Heliers, Jersey, in 

 May of the year 1878, in a jar of sea-water preserved for some weeks, containing 

 various protozoa and hydroid zoophytes collected on the adjacent coast. At first 

 sight the aspect presented by these animalcules so closely resembled that of the 

 ordinary members of the genus SpiimeUa or Oikomonas, Avith, perhaps, some little 

 extra haziness around the peripheral margin, that they were nearly passed over as 

 such, and it was not until the aid of a more powerful object-glass was brought to 

 bear upon them that their true nature became apparent. It was then demonstrated 

 that the hitherto hazy environment of the periphery of the body consisted of fine, 

 closely-set, slender pseudopodia radiating in every direction, agreeing in form and 

 structure with those of Acti)iophrys, Adinolophus, or any other typical Radiolaria, 

 and subservient to a closely similar function. Through its possession of a long 

 terminal flagellum, however, Actinomonas possesses considerable advantages over 

 such a type as Actinolophus. While the last-named form has to wait patiently for 

 the advent of food-particles within grasping reach of its tenacious pseudopodia, 

 Adinoniotias, by the vibrations of its flagellate appendage, draws towards it all such 

 substances floating in the vicinity, and throws them back among the pseudopodic 

 processes, by which they are immediately seized and dragged into the substance of 

 its body. The capture and ingestion of food-matter in this manner, at all parts of 

 the circumference, were witnessed on several occasions. Physiologically, the ex- 

 tended peripheral pseudopodia of Actinomonas are closely analogous to the exten- 

 sile sarcode collar of the Choano-Flagellate order hereafter described, a similar 

 trap-like function, in combination with the flagellum, being common also to that 

 diversely modified pseudopodic structure. The developmental and reproductive 

 phenomena of this remarkable type have yet to be determined. 



Actinomonas pusilla, S. K. Pl. I. Figs. 7 and 8. 



Body subspheroidal ; pedicle equal to, or very slightly exceeding in 

 length, the diameter of the body ; flagellum slender, extended rigidly and 

 arcuately from the apical extremity ; pseudopodia equalling in length the 

 diameter of the body, projected from all parts of the periphery, much 

 less numerous than in the preceding species. Diameter of body 1-3250". 



Hab. — Salt water. 



This species may be distinguished from the preceding by its more minute size, 

 the shorter comparative length of the pedicle, and the considerably less numerical 

 development of the radiating pseudopodia. It was obtained in some abundance in 

 sea-water containing Zoothanuiium dichotomtim attached to Fuci, remitted to the 

 author by Mr. Thomas Bolton from the Birmingham Aquarium in February of the 

 present year (1880). It was observed that the specimens often attached themselves 

 to the neighbouring vegetable debris by several radiating pseudopodia simultaneously, 



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