XL 



REMARKS ON CERTAIN PROBLEMS 

 OF THE DAY. 



The following essay was originally intended as an answer 

 to the criticisms which Professor Vines ^ brought forward 

 against certain of my views, shortly after the pubHcation, 

 in an English form, of a collected edition of those essays of 

 mine which appeared in Germany during the years 1881-1889 ^ 



This answer has been published in German because similar 

 objections have been urged by German writers, and I further 

 hope that this essay may perhaps serve to render clearer some 

 of the problems with which it deals. Much might have been 

 added on the points here referred to, but the occasion, and the 

 nature of the essay itself, called for a certain amount of restric- 

 tion, and enforced a concentrated treatment of the most impor- 

 tant subjects. 



Professor Vines commenced his article by a criticism of that 

 attribute of immortality which I have claimed both for unicel- 

 lular organisms and for the reproductive cells of multicellular 

 beings. If I rightly understand the English professor, he does 

 not contest the truth of this view, but he fails to find in my 

 book a satisfactory explanation of the process by which the 

 immortal organisms gave rise, in the course of their phyletic 

 development, to mortal descendants. The first difficulty which 

 presents itself is to understand how the mortal heteroplas- 

 tides can have been evolved from the immortal monoplastides 

 or homoplastides. The explanation of this process, given 

 in my book, is the only one which seems applicable to the 



^ ' Nature,' Oct. 24, 1889, p. 621 et seqq. 

 ^ See Vol. I of the present Edition. 



