PROTEIN UPTAKE IN AMOEBAE 613 



2. In vesicles containina; ferritin, the carrier substance appears to 

 become detached from the membrane proper, and to break up into 

 irregular masses. When the carrier substance is bound to methyl ferritin, 

 however, the entire layer maintains its structural integritv, is detached 

 from the membrane proper, and becomes highly folded and crumpled by 

 48 hr. 



3. The osmiophilic membrane which limits the vesicle remains intact. 

 No pores or holes are seen, but many microvesicles appear attached to the 



fe' 



outer or cytoplasmic side of the limiting membrane. Also, complex 

 membranous structures, resembling myelin figures, accumulate within the 

 original vesicle. 



4. Neither ferritin nor methyl ferritin particles are seen in any part of 

 the cell except the pinocytosis \'esicles. Even in amoebae which have 

 carried large numbers of vesicles for 48 hr., the ground cytoplasm, mito- 

 chondria, contractile vacuoles and nuclei are consistently free of ferritin or 

 methyl ferritin. The microvesicles, a few hundred Angstrom units in 

 diameter, which fill the cytoplasm and are intimately attached to the 

 pinocytosis vesicles, never have been found to contain ferritin or methyl 

 ferritin. 



