w must immediately suggest itself. From that time the
perpendicular direction is preserved with more or less regularity.
Immediately after the perpendicular hole is begun, a shorter opening to
the surface is needed for conveying the mud from the nest, and then the
perpendicular opening is made. Mud from this, and also from the first
part of the perpendicular burrow, is carried out of the diagonal opening
and deposited on the edge. If a freshet occurs before this rim of mud
has had a chance to harden, it is washed away, and no mound is formed
over the oblique burrow.

After the vertical opening is made, as the hole is bored deeper, mud is
deposited on the edge, and the deeper it is dug the higher the mound. I
do not think that the chimney is a necessary part of the nest, but
simply the result of digging. I carried away several mounds, and in a
week revisited the place, and no attempt had been made to replace them;
but in one case, where I had in addition partly destroyed the burrow by
dropping mud into it, there was a simple half rim of mud around the
edge, showing that the crayfish had been at work; and as the mud was dry
the clearing must have been done soon after my departure. That the
crayfish retreats as the water in the ground falls lower and lower is
proved by the fact that at various intervals there are bottled-shaped
cavities marking the end of the burrow at an earlier period. A few of
those mounds farthest from the stream had their mouths closed by a
pellet of mud. It is said that all are closed during the summer months.

How these animals can live for months in the muddy, impure water is to
me a puzzle. They are very sluggish, possessing none of the quick
motions of their allied _C. bartonii,_ for when taken out and placed
either in water or on the ground, they move very slowly. The power of
throwing off their claws when these are grasped is often exercised.
About the middle of May the eggs hatch, and for a time the young cling
to the mother, but I am unable to state how long they remain thus. After
hatching they must grow rapidly, and soon the burrow will be too small
for them to live in, and they must migrate. It would be interesting to
know more about the habits of this peculiar species, about which so
little has been written. An interesting point to settle would be how and
where it gets its food. The burrow contains none, either animal or
vegetable. Food must be procured at night, or when the sun is not
s