318 
MAYNARD M. METCALF 
EXPLANATION OF FIGURES 
Figures showing successive conditions of the contractile vacuole in one individual 
of Amoeba proteus. All are camera drawings of optical sections, except fig. 2, 
which is a view of the granules on the upper surface of the contractile vacuole, 
and all are magnified 337 diameters. 
The irregular contours of the original, very rapid sketches, made from the living 
changing structures, have not been altered in the final drawings. The vacuoles 
were in reality spherical except when flattened on one side by pressure against the 
pellicle or when in contraction. 
1 A typical full-sized contractile vacuole. 
2 The granules over part of the upper surface of a large vacuole, showing that 
they do not make an uninterrupted layer over a very large vacuole as they do over 
one of moderate size. 
3-23. Are consecutive stages in the expansion and contraction of the vacuole 
(two and one-half cycles). 
3 At 2:50^ p.m. The vacuole has nearly reached its fullest size, has pushed 
through the ectosarc and now lies with its granules touching the pellicle. 
4 At 2:o2 p.m. The vacuole is larger, its granules are pushed to the sides 
until the contour of the vacuole coincides with the pellicle, which is pushed out- 
ward. 
5 At 2:53 p.m. The vacuole has begun to contract. 
6 At 2-o3§ p.m. The vacuole has nearly disappeared. 
7 At 2:55 p.m. The vacuole has wholly disappeared except for the faintest 
trace among the granules. The granules which ormerly surrounded the vacuole 
as a single layer now form a considerable mass. 
8 At 2 :55j p.m. Two small vacuoles have appeared in the midst of the mass of 
granules. 
9 At 2 :56 p.m. The two vacuoles have united into one. 
10 At 2:57 p.m. This fusion vacuole is now larger, and another small vacuole 
is formed on the outer edge of the mass of granules. 
11 At2:57jp.m. Thefirst vacuole is still larger and the second has been taken 
into the mass of granules and has rapidly enlarged to the size of its neighbor. 
12 At 2:58| p.m. The two vacuoles shown in the last figure have now united 
and another one has formed nearer the ectosarc. 
