round wasp once built a nest beneath the brick pavement in front of
my door. The entrance of the nest was situated in the little sulcus, or
ditch, between two bricks. While the wasp was absent, I stopped the
entrance with a pellet of paper, and, when the little housekeeper
returned, she was nonplussed for a moment or two, when she discovered
that her doorway had been closed. The wasp, after examining the pellet
of paper, seized it with her jaws and tried to pull it away; but, since
she stood on the brick and pulled backwards (toward herself), the edge
of the brick interposed, and she could not dislodge the obstacle.
Finally, she got down into the little gully between the two bricks, and
pulled the pellet away from the opening of the nest without any further
trouble. Three times I performed the experiment, the wasp going through
like performances each time. At the fourth time, however, she went at
once into the little space between the bricks, and then removed the wad
of paper without difficulty. I stopped the hole five or six times after
this, but she had learned a lesson; she always got into the sulcus
between the bricks before attempting to remove the paper. She had
discovered the fact that she could not remove it when she stood upon the
surfaces of the bricks, owing to the interposition of their sides, and
that she could drag it away if she got down into the little ditch and
pulled the paper in a direction where nothing opposed. In this instance
there was not only conscious determination, but also a distinct
exhibition of memory. It took the wasp some time to learn that she had
to pull in a certain direction before she could remove the pellet of
paper; but when she had once learned this fact, she remembered it. And
this brings us to another quality of mind--memory--which will be
discussed in the next chapter.

CHAPTER III

MEMORY

In discussing memory as it is to be observed in the lower animals, I
think it best to divide the subject into four parts; viz., _Memory of
Locality_ (_Surroundings_), _Memory of Friends_ (_Kindred_), _Memory of
Strangers_ (_Other Animals not Kin_), and _Memory of Events_
(_Education_, _Happenings_, _etc._).

_Memory of Locality._--There can be no doubt but that the rhizopods
observed by Carter displayed memory of locality. He distinctly asserts
that he saw the actinophrys, after it had incepted a starch grain,
"crawl away to a good distance" and then return to the spore-cell fro