164 J. M. D. OLMSTED 
final regenerated form, but several specimens which fulfilled the 
conditions of Group D and had heads at right angles to the old 
median axis were larger than those which did not fulfill these 
conditions and retained their old polarity. 
Such a regenerated worm lives for days or even weeks without 
change, except a diminution in size, until it disintegrates. It 
rarely moves about in its dish, but when disturbed it moves rap- 
Fig. 6 Case similar to that of figure 5; a, showing region from which the piece 
was taken; b, 3 days after operation; c, 5 days; d, 7 days; e, 14 days. 
idly in the direction in which the head points, or in wide curves 
with the original posterior edge directed toward the center of 
revolution. 
During the first two or three days of the regeneration of these 
triangular pieces whose heads develop at right angles to the old 
long axis, accumulation of new material occurs along both anterior 
and posterior edges, but the amount along the anterior edge is 
usually the greater (figs. 5d, 6c, 7b). Morgan (’98), in speak- 
ing of the regeneration of right-angled triangular pieces, says, 
