XI.] PROBLEMS OF THE DAY. 79 



unsupported assumption such as this, than to say that it in- 

 volves a contradiction in terms \' By this Professor Vines 

 means that the eternal cannot, from its very nature, pass into 

 the mortal, as it must do, if the perishable soma is derived from 

 undying germ-cells. It is obvious that this objection rests upon 

 the same confusion between immortality and eternity which 

 has been already rendered clear. I do not wish to reproach 

 Professor Vines with regard to this confusion ; some years ago 

 I encountered the same objection, and did not at once see 

 where the answer lay. We have hitherto been without a 

 scientific conception of immortality : we must understand by 

 this term — not life without beginning or end— but life which, 

 when it has once originated, continues without limit, accom- 

 panied or unaccompanied by modification (viz. specific changes 

 in unicellular organisms, or in the germ-plasm of multicellular 

 forms). This immortality is a movement of organic material, 

 which always recurs in a cycle, and is associated with no force 

 that tends to arrest its progress, just as the motion of planets 

 is associated with nothing which tends to arrest their move- 

 ment, although it had a beginning and must at some future 

 time, by the operation of external causes, come to an end. 



Further on, Professor Vines says, 'I understand Professor 

 Weismann to imply that his theory of heredity is not— like, for 

 instance, Darwin's theory of pangenesis — "a provisional or 

 purely formal solution 2" of the question, but one which is 

 applicable to every detail of embryogeny, as well as to the 

 more general phenomena of heredity and variation ^' I have 

 indeed, in contradistinction to my own attempt to give a 

 theoretical basis to heredity, spoken of Darwin's pangenesis 

 as a purely formal solution of the question ; and perhaps I 

 may be allowed to give a short explanation of the expression, 

 for I fear that, not only Professor Vines, but many other 

 readers of my essays may have misunderstood me. On the 

 one hand I am afraid that they may have found in my words 

 a tacit objection to Darwin's pangenesis, an objection which 

 I did not at all intend, and, on the other, that I was inclined 

 to overstate the value of my own theor}^ 



There are, I think, two kinds of theory which may be con- 



1 ' Nature,' Oct. 1889, p. 623. 2 gee Vol. I, p. 168. 



3 ' Nature,' Oct. 1889, p. 623. 



