172 STUDIES IN GENERAL PHYSIOLOGY 
minimal size, is cut from Tubularia mesembryanthemum, 
and both its ends are surrounded by water, a head is formed 
at both ends (Fig. 16). The head is usually formed more 
rapidly at the oral than at the aboral end. In this way it is 
possible to produce any number of bioral animals without 
interfering with their vitality. 
b) If a piece of root is carefully separated from the base 
to which it was attached, so that it is surrounded on all 
sides by water, a head is formed at its aboral end. The root 
continues to grow but forms no polyps if it is allowed to 
attach itself anew as a root. 
2. Ifa portion of the stem is cut from Aglaophenia and 
suspended vertically in the aquarium, it always forms a root 
at its lower end, according to observations made thus far; it 
matters not whether the apical or the basal end is directed 
downward. Hither a tip or a root is formed at the end directed 
upward (toward the zenith), but a tip is formed the more 
readily when the apical end is directed upward. 
It is therefore possible to create biapical and bibasal 
forms (Figs. 17 and 18) in Aglaophenia; yet the certainty 
with which bibasal animals can be created is greater than 
that with which biapical animals can be produced. 
3. If the stems of Plumularia pinnata are cut off close to 
the root and fixed in a vertical position, but with the tip 
downward, a new tip instead of a new root may arise from 
the basal end, which continues to grow upward; more fre- 
quently a root first springs from this end, from which arises 
a stem that grows upward (Fig. 20, a, b). 
4a) If a piece is cut from the stem of Eudendrium, and 
both ends are surrounded by water, new tips are formed at 
both extremities (Fig. 21, a,b). Yet a variation occurs at 
times which I have not observed in the beforementioned ani- 
mals; namely, a new tip and a new root may grow from the 
same cut end. 
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