HETEROMORPHOSIS 131 
the nearer the tip they are. These points enable one to dis- 
tinguish between the basal end (originally directed toward 
the root) and the apical end (originally directed toward the 
tip) of a stem from which the tip and root have been cut. 
2. I cut off some stems of Aglaophenia pluma close to the 
pe 
FIG. 17 FIG. 18 FIG, 19 
root, and fixed them vertically, but with their tips down- 
ward, into the sand. The tips were planted just deeply 
enough to keep the animals in a vertical position. The 
remaining part of the stem was surrounded by water. Ina 
number of these animals new tips, which continued to grow 
upward, were formed at the basal ends (Figs. 18,19). At 
first the old main stem grew in length by growing vertically 
upward. From this there then arose the lateral branches. 
The new polyps which were formed grew only upon the 
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