GENUS ACTIN0SPI1/ERIUM— ACTINOSPn^RIUM KICHHORNII. 261 



perceptible as pale, shaded spots in the interior of the body. Dilute acetic 

 acid brings them into view as pale and faintly granular spheres, with a 

 large central nucleolus, or sevei'al smaller nucleoli. The smallest individ- 

 uals appear commonly to contain but a single nucleus, as in the common 

 Sun-animalcule. 



The pseudopodal rays project in all directions (figs. 1-3) as in the 

 latter, and are equally numerous. They are long, tapering extensions of 

 granular protoplasm, sustained by a delicate axial thread, but proportion- 

 ately are commonly not so long as in Actinophrys sol. 



The axial thread of the pseudopodal rays is a simple, comparatively 

 rigid, and straight filament, which starts from the surface of the interior 

 vesicular mass of the body, and passes through the peripheral layer of larger 

 vesicles between them. The threads extend through the greater part of 

 the length of the pseudopods, but do not reach their ends. 



A portion of the granular protoplasm of the pseudopods appears to 

 originate from the stratum immediately beneath the peripheral layer of 

 vesicles, and extends upon the axial thread through the latter, when it is 

 reinforced by an additional portion converging from the exterior investment 

 of the same material, as seen in fig. 7. 



The axial threads of the pseudopods are homogeneous, and appear 

 to consist of more or less solidified protoplasm. They clearly contribute to 

 sustain and strengthen the pseudopodal rays ; and, though they seem to be, 

 they are not rigid spicules, for they may be seen to bend beneath the 

 rude shock of active animalcules coming into contact with the rays. At 

 times, also, they appear not to be persistent structures, as I have observed 

 individuals in which they seemed to vanish with the retraction of the rays, 

 and again reappear with the production of these. 



Occasionally I have seen individuals of Actinosphaerium with few or 

 no rays. 



The food of Actinosphcerivm eichhornii in general is of the same nature, 

 and the mode of taking it the same, as in Actinophrys sol. With its usually 

 greater size and strength than in the latter, the former will feed upon larger 

 and more powerful animals, especially various rotifers. Though the animal 

 is to all appearances exceedingly inactive and sluggish, remaining sus- 

 pended in the water almost motionless or feebly gliding about, it is a glut- 

 tonous feeder and consumes a large amount of food. This commonly con- 



