XI.] PROBLEMS OF THE DAY. 79 



unsupported assumption such as this, than to saj'- 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 - " 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 mclined 

 to overstate the value of my own theory. 



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



1 ' Nature,' Oct. 1889, p. 623. ^ See Vol. I, p. 168. 



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



