HETEROMORPHOSIS 137 
stem upon the glass remained permanently the same, 
though the tip itself moved forward at the rate of about 
1mm. each day. The longitudinal growth must, therefore, 
have occurred in the narrow zone lying in front of the new stem. 
13. These experiments were made in April when the 
Aglaopheniw were sex- 
ually mature. One day I. 
observed a number of small 
(about 4mm. long), whitish, 
cone-shaped larvee that moved 
over the bottom of the 
aquarium toward the window, 
and remained there. The 
next morning, however, they 
had all disappeared, so that 
I can only suspect that these 
organisms, which in the 
moment of observation were 
positively heliotropic, may 
have been larvee of Aglao- 
phenia. 
€ 
VI. HETEROMORPHOSIS IN 
PLUMULARIA PINNATA 
1. I have made a series of 
FIG, 20a FIG. 20 = experiments, similar to those 
made upon Aglaophenia, upon Plumularia pinnata, which in 
form closely resembles Aglaophenia pluma. I wish to 
describe one of these experiments here. 
A series of stalks were cut off close to the root and fixed 
vertically in the sand, so that the apical ends were covered 
by it. In individual instances, but only very rarely, a new 
tip was immediately formed at the aboral end, so that I ob- 
tained biapical animals similar to those of Aglaophenia 
ae 
Digitized by Microsoft® 
