WALLACE O. FENlSf 587 



the cells. Only solitary cells were included in the count as it would 



be easy to overlook the colorless quartz particles in the aggregated 



cells. All the solitary cells in each field were examined. In all, 



9 quartz particles and 59 carbon particles were found ingested by 



some 200 to 300 cells which were examined. 



Since there were approximately twice as many carbon particles 



as quartz present, it may be concluded that carbon is ingested by 



59 . . 



sponge cells or 3 times as readily as quartz. This agrees well 



with the results with leucocytes. The sponge cells were not con- 

 sidered sufficiently phagocytic to justify more quantitative experi- 

 ments. 



DISCUSSION 



Whatever hypothesis is adopted to explain the more rapid ingestion 

 of carbon, it must be concluded that there is for some reason greater 

 attraction between the cell substance and the carbon than between 

 the cell substance and the quartz. In view of the high adsorptive 

 capacity of carbon this is not surprising, nor is this difference between 

 different kinds of solid particles without its parallel in inorganic 

 systems. Similar examples of selective "wetting" of solid particles 

 are found in the flotation processes for the separation of different kinds 

 of ores (8), which depend upon the fact that, in general, particles of 

 the heavy metals have a greater affinity for oil and air phases than 

 for water, and are thus floated to the surface while the worthless 

 gangue particles such as silicates remain in the water and sink. 



Rhumbler (9) remarks that the rhizopod Euglypha, in forming its 

 shell of small particles, is able to distinguish between different ma- 

 terials. In imitating this he rubbed up coal and quartz particles in 

 various oils and sprayed them into 70 per cent alcohol. In such 

 instances the coal remains on the inside of the oil drops and the quartz 

 collects in the surface. This observation being of considerable 

 interest for these experiments has been repeated quantitatively with 

 oil drops in 70 per cent alcohol and chloroform drops in water. In 

 all cases the carbon collects in the interface between the phases more 

 rapidly than the quartz. 



