REGENERATION AND DEATH 183 



serve for the reproduction of the species. These cells 

 are set apart at all periods. They represent germinal 

 matter which is withheld from the metamorphosis 

 which the rest of the body undergoes. They have 

 a continuous history. Hence we bestow upon this 

 method, under the conception that it is applied to 

 secure propagation of the species, the term theory 

 of germinal continuity. It is the theory of hereditary 

 transmission, which I think is now universally held 

 by all competent biologists. Our study of nuclei and 

 of their relations to protoplasm serves to clear up in 

 our minds, it seems to me, to some degree at least, 

 the necessity which really exists for this device of 

 germinal continuity, of the setting apart of certain 

 cells of the rejuvenating sort, of the young sort, of 

 the embryonic type (the term you apply to them 

 matters little), which cells are those used to produce 

 the new offspring of the next generation. All this, 

 of course, fits perfectly with the doctrine which I 

 have been telling you of again and again in this course 

 of lectures, that the progress of differentiation is al- 

 ways in one direction and ends in the production of 

 structure which, if it is pursued to its legitimate ter- 

 minus, results in the degeneration and death of the 

 cell. Obviously cytomorphosis cannot produce the 

 sort of a cell which is necessary for reproduction. 



I wish there were time to enter more fully into the 

 question of the size of nuclei, for there is much which 

 might be said concerning it. This much more, how- 

 ever, ought to be said to you that the problem of 



