STUDIES upox a:\ioeba 
MAYXARD :M. IMETCALF 
Professor of Zoology, Oberlin College 
FORTY-FIVE FIGURES 
I. OX THE LOCALIZATIOX OF THE EXCRETORY FUNCTION 
IX .AJMOEBA PROTEUS 
Casual observation of the contractile vacuole shows in most 
species of Amoeba no evidence of its having any constant relation 
to any particular portion of the protoplasm. As the animal moves 
along with its characteristic flowing motion, the excretory vacuole 
flows along with the rest of the body, apparently very much as 
does any gastric vacuole or foecal particle. At more or less ir- 
regular intervals the excretory vacuole contracts and disappears, 
to reappear again after a time. It is a question of some interest 
whether, when the vacuole reappears, it reappears within the same 
portion of protoplasm which surrounded it before its last contrac- 
tion. In most Amoebae the question is a difficult one to answer. 
But in some Amoebae proteus^ which we have used in our labor- 
atory in Oberlin this year and last, we find conditions that answer 
this question very definitely for us.- 
^ Either the species proteus includes very diverse individuals — diversent as to 
food habits, the condition of the crystals and plastids and plasma, and in the char- 
acter of the excretory vacuole, or we should distinguish in the diverse types two 
or more species, or subspecies if preferred. The Amoebae here studied feed almost 
wholly upon bacteria, have numerous crystals, often contain much paraglycogen, 
and have spheroidal plastids that I have not yet studied. The granules around 
the contractile vacuole are better defined than those of other Amoebae I have 
studied. 
^ These Amoebae were obtained from Prof. J. H. Powers of the University of 
Nebraska. 
