The Hypothesis of Formative Stuffs * 
By ‘TT. H. MorGAN 
It is with some hesitation that I venture to discuss the hypothe- 
sis of formative stuffs as used by Professor Goebel in his Organo- 
graphie and in his recent papers in the Biologisches Centralblatt. 
But since for all questions connected with the regeneration of 
plants it is of great importance to have a clear understanding of 
what this hypothesis really means, I hope that I shall be justified 
in entering into a discussion of this question, although the hypothe- 
sis is applied by its present adherents rather to plants than to ani- 
mals. Professor Goebel uses the word correlation to give a name 
to certain curious, connected changes in different parts of the plant. 
Almost without exception when he ventures to express an opinion as 
to the cause of this connection, he makes use in one form or another 
of the Bonnet-Sachs hypothesis of formative stuffs. These stuffs 
are imagined to be either organized or unorganized substances that 
flow in different directions. The cause of this flow is sometimes 
ascribed to the polarity of the tissues; at other times to the af- 
tractive power for such substances that certain parts are supposed 
to possess, These alternatives are, I believe, fundamentally different 
conceptions, 
I have made bold to question this hypothesis of formative 
stuffs.} More especially in the case of animals I have tried to 
show that there is little or no evidence in favor of such a view. 
In the case of plants I admit that under certain circumstances the 
presence or quantity of certain materials, especially food stuffs, may 
play a part in regenerative processes. But even in plants, despite 
the high authority by which the hypothesis is supported, I am 
sceptical whether formative stuffs are the chief factors in the result 
in those cases where polarity is involved. Let us examine the 
ne more carefully. Bonnet suggested, in 1745, that the 
* Read by invitation before the Botanical teeteis of America, at Wa daapial 
December 31, 1902, 
t Morgan, T. H. Regeneration, 88-90. 1901. 
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