86 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



At the present time there are also two fundamental and opposing 

 views of the nature of the "organization of the organism/' namely, 

 those in which "organization" is explained as the result of the col- 

 lective action of smaller units, and second, those in which the "or- 

 ganization" itself is regarded as a single unit which controls the 

 parts.* The more recent hypothesis of regeneration may be roughly 

 classified as coming under one or the other of these tw^o interpreta- 

 tions of the organism. 



The preformation theories of Bonnet and the germ theory of Weis- 

 mann are representative of the first school. Weismann, with Bonnet, 

 assumed the existence of latent germs in the different parts of the 

 body. But Weismann went further, and located these germs in the 

 nucleus of the cell. Regeneration, then, is caused by latent cells 

 which contain pre-formed germs in the nucleus, called determinants. 



Supporters of the other school, like Whitman and Morgan, strongly 

 argue that the cell theory is too narrow a basis from which to inter- 

 pret the organism, and that the organism has a structure of its own 

 independent of that of the cells. It is maintained, for example, that 

 such phenomenon as a certain "polarity," w^hich is well illustrated 

 in a piece of worm in which the anterior region always reproduces a 

 head and the posterior end a tail — that such phenomena must be 

 considered in an explanation of regeneration. At present a variety 

 of experiments are being made to determine in what way the new 

 regenerating material is "regulated" by the structure of the piece or of 

 the organism. 



Thus it may be seen that the question of regeneration is still an 

 open one, and that what is needed is a larger body of careful and 

 exact experiments and observations before we can hope for a final 

 solution of the problem. 



EXPERIMENTS AND OBSERVATIONS ON REGENERATION. 



Systematic observations were made and material collected during 

 the summer of 1904 at the experiment station of the Rhode Island 



♦Morgan. Regeneration, p. 277. 



