158 J. M. D. OLMSTED 
The species of planarian used in these experiments was Plan- 
aria maculata Leidy, and the specimens were taken from Fresh 
Pond near Cambridge, Mass. Worms of various sizes, from 12 
to 5 millimeters in length, were used. Some specimens, after 
being brought into the laboratory, were fed on liver until at the 
time of operation they were of the maximum size. Others, 
medium and small worms, were kept without food for several 
weeks. Neither the condition of satiety nor of starvation 
noticeably influenced regeneration. At one time the mortality 
of one lot would be greater, at another time, that of the other. 
In the fed worms, however, it was found best to allow one week 
to elapse after the last feeding before the operation was performed. 
To prepare the planarians for operation, they were narcotized 
in a 0.1 per cent solution of chloretone until they ceased to move. 
Cuts were then made with a sharp scalpel, care being taken to 
have the cut edges as nearly straight as possible. Triangular 
pieces were taken from all regions of the body, each triangle 
having for one of its sides a portion of the original uncut right 
or left margin of the worm, and, for the other two sides, cut edges 
which intersected near the original median axis of the worm (fig. 
2a, 5a, 7a). The two cut edges, intersecting at a point which 
I shall refer to as the vertex of the triangle, are distinguished in the 
following account as the anterior and posterior edges. 
It was only towards the end of experimentation that the im- 
portance of fairly exact measurements of the lengths of the cut 
and uncut edges, the angle where the cut edges meet, the distance 
of the vertex of this angle from the median axis of the worm 
from which the piece is taken, and the size of the piece, was 
realized. In the earlier part of the work, no camera drawings. 
were made until the day following the operation. Because of 
the decided contraction of the pieces at this time and the con- 
sequent distortion of their original shape, it was possible to 
estimate only rather roughly their original measurements. Later 
in the work, however, camera drawings were made immediately 
after operation while the pieces were still in chloretone, the very 
slight contraction in this condition being negligible; a second 
drawing of each piece was made on the day following, when they 
