No. 581] GERM CELLS AND SOMATIC CELLS 305 



may also lead to alterations in metabolism calling forth a 

 destructive activity of connective tissue and lymphocytes. 

 Thus there exist difficulties in the case of certain tissues 

 in demonstrating through serial transplantation their 

 potential immortality, in a similar manner as it lias been 

 demonstrated in the case of strongly proliferating somatic 

 cells (tumor cells). 



It is also shown that in the case of the germ cells which 

 really represent a foreign individual within a host organ- 

 ism mechanisms exist which prevent these injurious agen- 

 cies from becoming effective. 



3. "We must sharply distinguish between the power of 

 cells to grow and their power to live. While the former 

 seems to be destroyed through differentiation, the latter 

 may still exist, and we can therefore at present not deny 

 the possibility that even highly differentiated somatic 

 cells may still possess the potentiality of immortal life. 



4. While in the case of protozoa and germ cells definite 

 cycles exist, manifesting themselves either through the 

 occurrence of rhythmically occurring depressions of vital- 

 ity or of typical changes in the nuclei, such cycles have so 

 far not been demonstrated in the case of somatic cells, 

 particularly of tumor cells. 



5. In the case of germ, cells external factors can pro- 

 duce certain changes, and these changes (not necessarily 

 identical with those originally produced through the ex- 

 ternal factors) can be transmitted to the offspring. It is 

 shown that in a similar way in the case of somatic (tumor) 

 cells a transmission of characters acquired under the in. 

 fluence of external agencies to the succeeding cell genera- 

 tions may take place. It can be shown in the case of the 

 somatic cells that apparently similar changes produced 

 through different external agencies are really not iden- 

 tical, but specific. It is suggested that such a specificity 

 of transmitted characters may also exist in the case of 

 germ cells despite the apparent identity of changes pro- 

 duced through different external agencies. 



