Untitled

Body subspherical orGENUS ACTINOMONAS. 227Actinomonas mirabilis, S. K. PL. I. FIG. 18.ovate, seated on a slender pedicle, which usuallyequals two or three times the diameter of the body ; endoplasm transparent,slightly granular ; flagellum very long and slender, extended rigidlyand arcuately in advance ; pseudopodia equalling in length the diameterof the body, very numerous, radiating from all points of the periphery ;contractile vesicles two in number, situated close to each other in theposterior region of the body1-2000".HAB. Salt water.; endoplast spherical, subcentral. DiameterSeveral examples of this interesting type were met with at St. Heliers, Jersey, inMay of the year 1878, in a jar of sea-water preserved for some weeks, containingvarious protozoa and hydroid zoophytes collected on the adjacent coast. At firstsight the aspect presented by these animalcules so closely resembled that of theordinary members of the genus Spumella or Oikomonas, with, perhaps, some littleextra haziness around the peripheral margin, that they were nearly passed over assuch, and it was not until the aid of a more powerful object-glass was brought tobear upon them that their true nature became apparent. It was then demonstratedthat the hitherto hazy environment of the periphery of the body consisted of fine,closely-set, slender pseudopodia radiating in every direction, agreeing in form andstructure with those of Actinophrys^ Actinolophus, or any other typical Radiolaria,and subservient to a closely similar function. Through its possession of a longterminal flagellum, however, Actinomonas possesses considerable advantages oversuch a type as Actinolophus. While the last-named form has to wait patiently forthe advent of food-particles within grasping reach of its tenacious pseudopodia,Actinomonas, by the vibrations of its flagellate appendage, draws towards it all suchsubstances floating in the vicinity, and throws them back among the pseudopodicprocesses, by which they are immediately seized and dragged into the substance ofits body. The capture and ingestion of food-matter in this manner, at all parts ofthe circumference, were witnessed on several occasions. Physiologically, the extendedperipheral pseudopodia of Actinomonas are closely analogous to the extensilesarcode collar of the Choano-Flagellate order hereafter described, a similartrap-like function, in combination with the flagellum, being common also to thatdiversely modified pseudopodic structure. The developmental and reproductivephenomena 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 inlength, the diameter of the body ; flagellum slender, extended rigidly andarcuately from the apical extremity ; pseudopodia equalling in length thediameter of the body, projected from all parts of the periphery, muchless 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 numericaldevelopment of the radiating pseudopodia. It was obtained in some abundance insea-water containing Zoothamnium dichotomum attached to Fuci, remitted to theauthor by Mr. Thomas Bolton from the Birmingham Aquarium in February of thepresent year (1880). It was observed that the specimens often attached themselvesto the neighbouring vegetable debris by several radiating pseudopodia simultaneously,Q 2