IV 
HETEROMORPHOSIS! 
I. INTRODUCTION 
Ir is well known that a number of animals possess the 
power of forming a new organ in the place of an organ which 
has been lost. It has always been taken as a matter of course 
in animal physiology that the regenerated organ is neces- 
sarily identical in form and function with the one which has 
been lost. The experience of the botanists, however, shows 
that this does not hold true in the case of plants, and a few 
sporadic observations upon animals—which, however, have 
not been taken into consideration for this problem—seemed 
to suggest that similar conditions might be found in animals. 
I have undertaken the task of finding out whether and by 
what means it is possible in animals to produce at will in 
the place of a lost organ a typically different one—differ- 
ent not only in form, but also in function. It is my purpose 
to report the results of these experiments in the following 
pages. 
The organs which I tried to substitute for each other in 
these experiments are the oral and aboral poles (head and 
foot). I have succeeded in finding animals in which it is 
possible to produce at desire a head in place of a foot at the 
aboral end, without injuring the vitality of the animal. The 
animal shown in Fig. 16, a Tubularian, has by artificial means 
been so altered that it terminates in a head at both its oral 
and aboral ends. If, for any reason, it were necessary to 
create any number of such bioral Tubularians, this demand 
could be satisfied. In another Hydroid, Aglaophenia pluma, 
1 Warzburg, 1891. The pamphlet is dated 1391, although it appeared in 189, 
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