3 i8 AUGUST WE ISM ANN [ai-kil 



study as practised by Oken, Schelling, and others in the beginning of 

 this century, one should surely recognise the difference that exists 

 between this juggling with ideas and a priori interpretation and my 

 attempts to gather all the facts together under a common point of 

 view. The former are mere fantasies which will never establish 

 anything, the latter are, to some extent, central points for scientific 

 tasks which will yield to the investigator provisional assumptions to 

 be corroborated or disproved : they may even give into his hand 

 biological formulae or symbols which, though incapable of full ex- 

 planation as yet, may with advantage be included in the consideration 

 of certain problems. 



When Oken, for instance, says " the contrasts in the solar-system 

 between the planets and the solar bodies repeat themselves in plants 

 and animals, and as light is the principle of movement, the animal 

 has the power of independent movement as an advantage over the 

 plaut organisms which are fixed to the earth," no one will attempt to 

 make anything of it, altogether apart from the fact that the tertiwm 

 comparationis immobility, as we now know, is not peculiar either to 

 the sun or to the plants. Again, Oken, with true prevision, stated 

 that " everything organic has come from slime, and is nothing but 

 slime in various forms ; this primitive slime had its origin in the sea 

 in the process of the development of the planets from inorganic 

 material " ; and then the primitive slime took the form of little vesicles, 

 and " the whole organic world has as its basis an infinity of such 

 vesicles." These are a priori interpretations of nature which by 

 chance come very near the truth, but which, when they were put 

 forward, could not in the smallest degree further the progress of 

 knowledge, because no one then possessed the means of proving them 

 right or wrong, or of deriving from them any deeper insight into the 

 process of life. But, on the other hand, the " supposition " advanced 

 in the " Germ -Plasm," that regeneration may be an adaptation - 

 phenomenon and as such depends upon processes of selection, is not 

 a final verdict but simply a hypothesis which may give a new lead 

 for investigators to follow, as Morgan himself has done. 



Conclusive results, of course, cannot always be obtained from a 

 single series of experiments, for Nature's answer to our questions is not 

 usually capable of only one interpretation, and criticism is often neces- 

 sary in order that it may be read correctly. Thus Morgan's results do 

 not afford a convincing refutation of my theory of the adaptive nature 

 of regeneration ; they have even, indeed, a bearing which tells decidedly 

 in favour of my view. If the provisional conclusion that the almost 

 rudimentary abdominal appendages are regenerated less frequently than 

 the actively functional walking legs is corroborated, it, at any rate, will 

 be intelligible from the standpoint of the selection-interpretation, but 

 not from that of those who regard the organism as a crystal, and 

 regeneration as an inevitable completion of the crystallisation. For if 



