NESTS OF PSEUDOSCORPIONES., 103 
spaces under the bark of partly dead oaks; and the cells in 
which they were placed were provided with strips of decayed 
wood from these trees. The arrangement was such that narrow 
spaces were left between the strips of wood and the glass of 
the cells. Colonies thus established—strengthened by fresh 
importations from time to time—-were under observation for 
two years; and at the time of writing, two cells contained 
together eleven nests: some on the floors of the cells, with a 
complete convex roof, and others of more compressed form in 
the spaces between the wood and the glass. 
At various seasons certain of the animals, either young or 
adult, became distended—no doubt from accumulated nutritive 
matiers—and it was in this condition that they enclosed them- 
selves either for moulting, for brood-purposes, or for the winter. 
Such an individual restlessly perambulated the cell, investigating 
the corners and crevices, every now and then picking up with 
the palp-fingers and removing dead insects and other scattered 
objects; and occasionally, at such times, it detached fragments 
from the wood, taking hold of them with the palp-fingers and 
using considerable force. It was evidently prospecting for a 
position for the nest. At length, having decided on one, it 
was soon at work on it with the chelicere, and usually by the 
following morning or evening it had arranged round itself a 
complete ring of fragments of wood, ete. It was now unsafe 
to abandon the post of observation, for the animal got to work 
with rapidity and within about twelve hours had generally 
completed the external coating or framework of the nest, the 
builder being then—except in those cases in which the glass 
formed the roof—entirely concealed from view. 
The manner in which the animal constructed this framework 
and enclosed itself within was the subject of numerous obser- 
vations. But the procedure may be indicated by taking the 
case of the making of a brood-nest with a complete convex 
roof, the observation of which extended almost from beginning 
to end. The distended builder was restlessly moving about im 
the morning, and in the evening of the same day was found 
to have taken up a position on the floor of the cell, where it 
had already surrounded itself with a ring of fragments. These 
were of wood and cork and mostly small—sawdust from the 
borings of Dryocetes villosus for the most part—and they were 
all definitely placed in position and seeured from within to the 
floor and to each other by threads of silk. They formed already 
the beginnings of the narrow circular wall of the nest. This 
was at 6 P.M., at which time the animal was within the circular 
space and full of business. For the continuation of its work 
it would require evidently a quantity of material, much of which 
would have to be procured from a distance. Coming up close to 
the wall, the animal extended the palps over it and felt about for 
fragments on the floor beyond. Finding some, it withdrew and 
proceeded with its work; or, failing to find any, it stepped over 
