With a high microscopic power, many bodies besides the digesting vacuoles and pulsating vesicles may be seen imbedded in the sarcode of the Amœba princeps; namely, coloured molecules, granules, fat-globules, and nuclei. All these bodies were seen by Mr. Carter, in certain Amœbina he found at Bombay, together with what he believed to be female reproductive cells, and motile particles similar to spermatozoids, or male fertilizing particles.
Fig. 87. Actinophrys sol.—A, ordinary form; B, act of division or conjugation; C, process of feeding; D, discharge of fæcal matter, a and b; o o, contractile vesicles.
The Actinophrys, a genus of the order Radiolaria, differs from the Amœba princeps in having a definite nearly spherical form with slender root-like filamental pseudopodia radiating from its surface in all directions as from a centre. They taper from the base to the apex, and sometimes end in knobs like a pin’s head, but vary much in length and number, and can be extended and retracted till they are out of sight. They are externally of a firmer substance than the sarcode of the body, which is merely a viscid fluid inclosed in a pellucid film. The Actinophrys sol, which is the type of the genus, is a sphere of from 1⁄1300 to 1⁄650 of an inch in diameter, with slender contractile filaments the length of its diameter extending from its surface as rays from the sun. It can draw them in and flatten its body so as to be easily mistaken for an Amœba. This creature, which is common in fresh-water pools where aquatic plants are growing and even in the sea, has little power of moving about like the Amœba; it depends almost entirely on its pseudopodia for food. They have an adhesive property, for when any animalcule or diatom comes in contact with one of them, they adhere to it; the filament then begins to retract, and as it shortens the adjacent filaments apply their points to the captive, enclose it, coalesce round it, the whole is drawn within the surface of the Actinophrys, the captive is imbedded in the sarcode mass, and passes into a vacuole where it is digested, and then the pseudopodia thrust out the undigested matter by a process exactly the reverse of that by which the food was taken in (D [fig. 87]). The pseudopodia are believed by Professor Rupert Jones to have the power of stunning their prey, for if an animalcule be touched by one of them, it instantly becomes motionless, and does not resume its activity for some time. The pulsations of the contractile vesicle are very regular, and its duty is the same as in the Amœba princeps.
The Actinophryna are propagated like the lowest vegetables by gemmation and conjugation, shown in B [fig. 87]; moreover Mr. Carter saw the production of germ-cells and motile particles in the Actinophrys exactly after the mode already described in the Amœba.
Mr. Carter mentions an instance in which the Actinophrys sol showed what may possibly be a certain degree of instinct. An individual was in the same vessel with vegetable cells charged with particles of starch; one of the cells had been ruptured and a little of the internal matter was protruded through the crevice. The Actinophrys came, extracted one of the starch-grains, and crept to a distance; it returned, and although there were no more starch-grains in sight, the creature managed to take them out from the interior of the cell one by one, always retiring to a distance and returning again, showing that it knew its way back, and where the starch-grains were to be found. On another occasion Mr. Carter saw an Actinophrys station itself close to the ripe spore cell of a plant, and as the young zoospores came out one after another, the Actinophrys caught every one of them even to the last and then retired to a distance as if instinctively conscious that no more remained. Like Amœbæ these animals select their food, but notwithstanding the superior facility and unfailing energy with which they capture prey larger and more active than themselves, they are invariably overcome even by a very small Amœba which they avoid if possible. When they come into contact the Amœba shows unwonted activity, tries to envelope the Actinophrys with its pseudopodia, but failing to capture the whole animal it tears out portions and conveys them to improvised vacuoles to be digested. Dr. Wallich mentions that he had seen nearly the half of a large Actinophrys transferred piecemeal to the interior of its enemy, where it was quickly digested.
Fig. 88, p. 19.
ACANTHOMETRA BULBOSA.
As every part of the body of the Actinophrys is equally capable of performing the part of nutrition, respiration, and circulation; and as in the absence of muscles and nerves they may be presumed to have no consciousness, the marks of apparent intelligence can only be attributed to a kind of instinct, and their motions to the vast inherent contractility of the sarcode and its enclosing film, which is also the case with the Amœbæ.