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 aerated 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 r6le in bringing about this result.) In what follows we 

 shall consider only the new growths which occurred at the 

 Tipper 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. 21a 

 and 216 ab is the old stem, be the regenerated tip, and ad 

 the heterornorphic 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 l 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 with a "polarity" which is determined 

 solely by internal structural relations, but with the effects of 



