XXXI 



ON THE TRANSFORMATION AND REGENERATION OF 



ORGANS l 



SEVERAL of the older scientists, for instance, Bonnet, 

 Spallanzani, and Dalyell had occasionally observed that in 

 the place of a head a tail may be regenerated in lower 

 animals. 2 These casual observations had been considered as 

 curiosities or pathological cases, and scientists took no further 

 notice of them. It occurred to me that it might be possible 

 to produce the substitution of one organ for another at 

 desire, and that in this way we might gain an insight into 

 the physiology of morphological processes. Having tried 

 in vain to accomplish this result during the year 1888 in 

 Kiel, I succeeded the following year at Naples. I found 

 that if the foot of a Tubularian be cut off and the foot 

 end of the stem surrounded on all sides by sea-water a head 

 will be produced instead of a foot, while the same end 

 produces a foot if it is in contact with some solid body, 

 like the bottom of the aquarium. This arbitrary substitu- 

 tion of one organ by another I called heteromorphosis in 

 contradistinction to the case of regeneration in which the 

 same organ is reproduced. I succeeded in showing that 

 phenomena of heteromorphosis can easily be produced in all 

 kinds of Hydroids and in Tunicates. 3 



Since then a great number of heteromorphoses in various 

 classes of animals have been obtained. The most brilliant 

 accomplishment in this field of science is undoutedly 

 Herbst's discovery that if in Crustaceans the eye together 



1 American Journal of Physiology, Vol. IV (1900), p. 60. 



2 Part I, p. 115. 3 LOC. cit. 



627 



