262 FRESHWATER RHIZOPODS OF NORTH AMERICA. 



sists of ciliated and flagellated infusoria, rotifers, zoospores, diatoms, the 

 smaller desmids, etc. 



Large active animalcules rudely brush against the multitudinous rays 

 of Actinosphaerium, and turn them aside without apparent harm to either, 

 and without the Actinosphaerium displaying any evident mark of irritability, 

 either in its rays or body. Weaker animalcules, coming within the influence 

 of the rays, are often rendered more or less powerless, or their movements 

 become enfeebled and finally cease. Being gradually drawn toward the 

 body by the retraction of one or more of the rays, the prey becomes im- 

 mersed in a mass of projected protoplasm, as seen in figs. 1, 2, c, which is 

 then gradually withdrawn with the included food. It passes through the 

 peripheral layer of large vesicles, and sinks among the mass of smaller 

 vesicles within. In the interior of the latter, food of various kinds is often 

 visible. Comparatively soft food, when swallowed quickly, assumes the 

 form of a ball, and is commonly seen in this condition, included within a 

 drop of clear liquid, in the interior of the body. More consistent food, such 

 as diatoms or the hard parts of rotifers, retains the original form. The food 

 is rapidly digested, undergoing changes, according to its nature, as in other 

 Rhizopods, and as repeatedly indicated in the preceding pages. 



Excrementitious matter, usually in the form of a ball, is discharged, by 

 a somewhat quick projection of a portion of the interior protoplasm of the 

 body containing the ball, through the peripheral vesicular layer, as repre- 

 sented in d, fig. 2. 



As above indicated, Actinosphcerium eichhornii may appear with few or 

 no rays. Fig. 4 represents an individual, which, when first observed, 

 possessed but a single long ray. After a brief interval, a second, and then 

 a third, were projected, and after an hour had elapsed it presented many 

 rays directed from all parts of the surface of the body. 



I once met with a singular body, of vesicular constitution and rayless, 

 as represented in fig. 6, which I supposed to be a rayless form of Actino- 

 sphcerium eichhornii. It was irregularly oval, and about 0.4 mm. long. 

 The peripheral vesicles were less uniform than in the characteristic forms 

 of Actinosphaerium, and had their greater diameter mostly in a reverse 

 direction from the usual one. Though entirely rayless, the animal showed 

 some activity, displayed in feeble changes in the outline of shape, and in 

 the slow expansion and quick collapse of some of the larger vesicles of the 



