214 
opening grew larger as the protoplasm flowed through and this flowing 
did not take more than three or four seconds to be completed. From 
the behavior of the other Amoebae which were on the slide and which 
as stated above had been touching and then separating I had anticipated 
some such action as this and was fortunate enough to have sketched the 
two which I saw unite, as they were moving toward each other, and as 
they united (fig. 1a—e). These drawings were made by the double vision 
method under the high power of the microscope (265 diameters), and 
with respect to shape and relative size are fairly accurate, although I 
was unable in either Amoeba to distinguish the nucleus. 
This union I believe to have been Copulation!. It was not a tem- 
porary union or contact, neither was it an engulfing or devouring of one 
Amoeba by the other. The two individuals were of nearly the same size 
and the process was a distinct and rapid flowing of the protoplasm of 
one into the protoplasm of the other, the resulting individual being a 
slightly larger Amoeba. The abundance of food contained in the 
Amoebae made this flowing all the more plainly visible, and enabled 
me to see clearly the definite currents as indicated by the arrows (fig. 1d). 
The transfer of protoplasm was plainly seen to be complete, none being 
cast off in the process, for the Amoebae at the time of copulation were 
in a clear field and there was no chance of confusion arising from the 
presence of other objects in the field. 
The only noticeable differences between the two Amoebae that 
copulated were the differences in shape and the fact that individual 
B (fig. 1) was the more active of the pair while A was less active. These 
factors may be unimportant although there is some relation between 
form and movement, the form of B (fig. 1b) being the form taken by this 
species of Amoeba in moving in a definite direction, while the form of 
A (same figure) is that taken by the Amoeba when moving less rapidly 
and in no definite direction. In this case copulation was accomplished 
by the protoplasm of the less active flowing into the protoplasm of the 
more active individual. The afternoon of the following day I observed 
this copulation process again in two other pairs, and in one of these 
(fig. 2) the movement of the protoplasm was again from the distinctly 
less active to the distinctly more active individual. In the third pair 
observed (fig. 3) both Amoebae were more nearly alike in activity and 
in shape, and, although I could not tell, which was the more active in 
this case, the process of copulation was the same as in the other two 
pairs. Whether this flowing from the less to the more active individual 
1 The German usage is here followed, and as the union of the gametes is com- 
plete and not partial and temporary, the word copulation instead of conjugation is 
used. 
