378 SCIENCE PROGRESS. 



struction of the lost part is impossible. If an Infusorian 

 cell, for example, of a very characteristic and complicated 

 form is cut in such a manner that only the one half retains 

 the nucleus, all the cell particles requisite to life are to be 

 found in this half, and these, through metabolism, will soon 

 reproduce the original shape of the cell. The metabolism 

 of the other half, on the contrary, having been permanently 

 injured, it will slowly die, being incapable of regeneration. 

 This important fact has been proved by a great number 

 of experiments made by Nussbaum, Gruber, Balbiani, and 

 others. 



We thus find metabolism to exist in the closest causal 

 relation with the production and preservation of form, and 

 in all investigations and experiments on the mechanism of 

 form-evolution it must not be lost sight of as constituting an 

 important factor. 



Max Verworn. 



