140 STUDIES IN GENERAL PHYSIOLOGY 
upon beakers. While the upper end of the animal was, 
therefore, in the-aquarium, in which the sea water was con- 
tinually renewed, the lower ends of the stems dipped into 
the beakers in which the circulation of the water was much 
less perfect than in the rest of the aquarium. Striking 
differences existed between the new growth which occurred 
at the lower end and that at the opposite end. The lower 
end in the poorly aérated water formed a new polyp upon 
the main stem, but its growth was slow, and the formation 
of new lateral branches occurred either not at all or only 
slightly as compared with the corresponding processes at the 
other end. (Possibly light and gravity may also have played 
a role in bringing about this result.) In what follows we 
shall consider only the new growths which occurred at the 
upper end of the vertically standing stem. 
2. When the basal end of the stem was directed upward, 
and new side branches were formed, they were directed, not 
toward the old tip, but toward the new tip. In Figs. 2la 
and 21b ab is the old stem, be the regenerated tip, and ad 
the heteromorphic tip at the aboral end. The newly formed 
branches s are all directed toward the heteromorphic tip d. 
In a larger number of cases new stems were formed also 
upon the old lateral branches after the stem had been turned 
upside down. Some of these did not grow downward toward 
the old tip, but in the opposite direction, upward, toward 
the new tip. Fig. 216 illustrates such an instance. After 
the whole stem had been suspended in an inverted position 
in the aquarium, a new branch s, was formed upon the 
lateral branch e, and grew upward, toward the new tip. It 
had, moreover, been formed upon the upper surface of the 
branch e. 
In the arrangement of new organs in Eudendrium we do 
not, therefore, deal witha “polarity” which is determined 
solely by internal structural relations, but with the effects of 
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