NOTES ON REGENERATION AND HETEROMOR-— 
PHOSIS OF TUBULARIAN HYDROIDS. 
ELIZABETH E. BICKFORD. 
CONTENTS. 
PAGE 
TL. INTRODUCTION .....cccccssecsesecceeceeeceeeeeecetsseeteceesescrnsssanansessaessanceasseecssrecearseenessesers 417 
TI. PROCESSES OF REGENERATION .....cs-:c-ccsee cescessecesseeesssseseessaecereccsense: teasers aces 418 
III. REGENERATION OF TRANSVERSE SECTIONS OF TUBULARIA ....---..-.---5 423 
IV. REGENERATION OF LONGITUDINAL SECTIONS OF TRUBU LARA -ccsecec2- 427 
CONCLUSION: occcseccssce-ci.cssscececceerecatcseeys-andonsecetaseeseangeehseeeenententetecetnetesssezercote=s ilsgstee 428 
LITERATURE CONSULTED. ......-2..:::::0ccecceteeeeeere tees Eee ere ere een 29 
I. INTRODUCTION. 
Tur regenerative power of Hydra was first studied by 
Trembley in 1744. He observed the general appearance of 
the healing, and the subsequent regeneration of pieces, obtain- 
ing fully formed hydras in a few days after they were cut. 
Nussbaum and Ischikawa (12) have since repeated and con- 
firmed his experiments. They found, as did Trembley, that 
the character and position of the regenerated organ is prede- 
termined in the uninjured animal, and that consequently 
tentacles always grow from the anterior end, and the foot 
from the posterior end of the cut portion. More recently, 
Jacques Loeb (10, 11) has confirmed these conclusions by 
experiments described fully in his work on “ Heteromorphosis ”’; 
he has shown that this law of predetermined orienta- 
tion holds good not only for the Hydra, but for many other 
forms of animals with which he experimented. But he has 
also shown that there are animals in which, as in certain 
plants, it does not hold good ; in these the position of the 
organs can be varied by external conditions. For example, he 
has shown that roots could be readily produced on oral ends 
of hydroid stems by simply bringing the regenerating end in 
