442 THE AMERICAN NATURALIST. {VOL XXXII. 
same box will call out the fighting reflex of dozens, which soon 
surround it, endeavoring to get in. The relative amounts of the two 
“nest materials ” seem to determine the reflex. The actions usually 
explained through “love,” “compassion,” or “hate” are better 
explained on purely physiological grounds. 
In pupz the “nest material ” is not yet differentiated, for all pupa 
will be eagerly accepted by all ants. As the pupz grow, their “ nest 
material ” mixes with that of the foster colony and the whole is modi- 
fied. A colony of more than one species is thus formed, examples 
of which are found in slave-making ants. The slaves of a nest will 
not be received if placed in the nest from which taken. They do not 
know their masters, nor do the masters know the slaves. They have 
become one colony through the mixing of their “ nest materials.” 
From the foregoing it appears that the different reactions of ants 
toward individuals of their own and different nests depend on 
reflexes. 
The next question that the author considers is: 
“ How do ants find their way?” 
It is generally thought that ants know the region about the nest, 
and orient themselves when going about by familiar objects, either 
through sight or smell. They travel on paths, and when off the path 
are lost until it is regained. Some sugar was placed on a blackened 
paper in front of anest. The first foraging ant did not find the sugar ; 
the second ant, after making many curves, zigzags, and loops, found 
the sugar, took a grain and retraced its steps, but cut off the loops. 
Before it had reached home a third ant had come to the place on the 
paper where No. 2 had left it, followed its track to the sugar, and 
returned the same way; and all ants which came near this path 
followed, each straightening it, however, by an antenna’s length, 
until in an hour or two there was a straight path between the nest 
and the sugar. None followed the unsuccessful trail. It would appear 
from this that not only is a track left which may serve as a guide to 
other ants, but which is of such a nature as to indicate the outcome 
of the expedition. The paths were followed as well when covered 
with black paper tunnels as if left well lighted, but a strip of paper 
5—1o mm. wide laid flat across a path would bother the ants greatly. 
-They would stop on reaching the paper, become very unquiet, several 
would collect on both sides, but none would cross over; some would 
turn and go back, some try to crawl under the paper. Something is 
deposited on the path which guides them, the volatile nature of which 
is shown by the fact that if the strip of paper is allowed to remain 
