PINOCYTOSIS l6l 



which we interpreted to indicate that the permeabihty of the vacuolar 

 membrane is changed after interiorization, with the effect that at least some 

 of the substances confined in the vacuoles can penetrate into the cytoplasm. 

 How this penetration occurs, and whether or not it involves some sort of 

 a breakdown, could not be decided by our experiments. 



Thus, while there are some indications that a change in the membrane 

 of the pinocvtosis vacuole occurs during its migration to the interior of the 



Fk;. 3. Electron micrograph of pinocvtosis channel in Amoeba proteiis, 

 showing micropinocytic vesicles and mitochondria close to the channel. (After 

 Chapman- Andresen and Nilsson [S].) 



cell we can from the evidence so far discussed derive no hint as to how this 

 change might be brought about. I believe, however, that this question may 

 be answered in time, when we know more about another problem of 

 pinocytosis which I should now like to discuss. It concerns the relationship 

 between pinocytosis vesicles and certain of the cytoplasmic structures 

 inside the cell. 



There are at present two main schools of thought regarding this 

 question. One connects the pinocytosis vesicles with the lysosomes, the 

 other with the endophisfiiic rcticith/iii, and I shall try very briefly to outline 

 the two views. 



