TWELFTH LECTURE. 



REGENERATION: OLD AND NEW 

 INTERPRETATIONS. 



T. H. MORGAN. 



The great interest that was awakened in the last century 

 in the study of regeneration was the result of the experiments 

 of Trembley, Reaumur, Bonnet, and Spallanzani. The interest 

 aroused through the work of these four naturalists has not 

 decreased, although from time to time other problems have 

 come to the front and attracted the attention of investigators. 

 More particularly in our own time has attention been directed 

 to problems connected with the egg and its development. But 

 it is becoming clearer, I think, that development by means of 

 an egg and development by means of regeneration cannot be 

 considered as separate and different phenomena, but at bottom 

 have many factors in common. There can be little doubt that 

 the results in one of these fields of study will throw light on 

 the other. It will be possible for me to consider at this time 

 only the suggestions and hypotheses advanced in connection 

 with the problems of regeneration. At another time I shall try 

 to compare these interpretations with those connected with the 

 development of the egg. 



Trembley's experiments on Hydra were the starting-point for 

 the three other naturalists. Spallanzani occupied himself mainly 

 with collecting new facts, while his friend Bonnet, who also 

 made many new observations of great value, seems to have 

 been more interested in the theoretical side of the problem. 



Bonnet supposed that regeneration was brought about through 

 the development of preformed germs. These germs exist in the 



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