40 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



ceptible kind, such as are commonly to be detected in a favorable light and 

 with the highest microscopic powers, in the clear limiting ectosarc, to such 

 as are distinct, darkly defined, and resemble the finest molecules of oil. 



2. Variable quantities of rather large, spherical, homogeneous, or indis- 

 tinctly granular corpuscles, usually colorless or faintly yellowish, apparently 

 liquid or semi liquid. 



3. Different proportions of round, oval, or irregularly oval bodies of 

 various sizes, clear, colorless, and highly refractive, apparently of the nature 

 of starch-granules, and resembling them in their chemical reaction. 



4. Variable quantities of round or oval globules darkly defined and 

 highly refractive, clear and colorless, or of different shades of yellow, 

 passing at times into brown, apparently oleaginous in character. These are 

 often altogether absent. 



5 Widely different proportions of food-balls, mostly spherical and of 

 pretty uniform size, and very variable in composition and color, according 

 to the nature of the food and the changes it has undergone through diges- 

 tion. The colored balls are commonly pale yellow, passing to darker 

 yellow and different shades of brown, even sometimes approaching to black- 

 ness. Often some of the balls appear bright green or yellowish green, 

 and are frequently recognizable as being- composed of round single-celled 

 algae. 



Generally the food-balls appear surrounded wilh a clear halo indicating 

 the presence of liquid enclosing the more solid matter, and consisting of 

 water swallowed with the food. Often the balls exhibit no vestige of such 

 a halo, in which cases we may infer that the water which may have been 

 swallowed with the food and had surrounded the ball, in an altered condi- 

 tion, has been imbibed by the including endosarc. 



Besides the more solid food-balls, there are frequently to be observed 

 globules of colored or colorless liquid or semi-liquid matters, which may 

 consist of water-drops swallowed as such, and of dissolved food resulting 

 from digestion. 



Sometimes large numbers of clear water-drops are not only seen within 

 the endosarc, but are actually observed to be developed as if from a con- 

 centration of the more liquid part of the protoplasm, and these are again 

 often seen slowly to disappear as if gradually absorbed by the contiguous 

 protoplasm. 



