PROFESSOR WEISMANN'S THEORIES. 477 



gate, no matter of what kind, inevitably end in a state of equi- 

 librium. Suns and planets die, as well as organisms. The process 

 of integration, which constitutes the fundamental trait of all evo- 

 lution, continues until it has brought about a state which nega- 

 tives further alterations, molar or molecular a state of balance 

 among the forces of the aggregate and the forces which oppose 

 them.* In so far, therefore, as Prof. Weismann's conclusions 

 imply the non-necessity of death, they can not be sustained. 



But now let us consider the above-described antithesis between 

 the immortal Protozoa and the mortal Metazoa. An essential part 

 of the theory is that the Protozoa can go on dividing and subdi- 

 viding without limit, so long as the fit external conditions are 

 maintained. But what is the evidence for this ? Even by Prof. 

 Weismann's own admission there is no proof. On page 285 he says : 



" I could only consent to adopt the hypothesis of rejuvenescence [achieved by 

 conjugation] if it were rendered absolutely certain that reproduction by division 

 could never under any circumstances persist indefinitely. But this can not be 

 proved with any greater certainty than fehe converse proposition, and hence, as far 

 as direct proof is concerned, the facts are equally uncertain on both sides." 



But this is an admission which seems to be entirely ignored when 

 there is alleged the contrast between the immortal Protozoa and 

 the mortal Metazoa. Following Prof. Weismann's method, it 

 would be " easy to imagine " that occasional conjugation is in all 

 cases essential ; and this easily imagined conclusion might fitly be 

 used to bar out his own. Indeed, considering how commonly con- 

 jugation is observed, it may be held difficult to imagine that it 

 can in any cases be dispensed with. Apart from imaginations of 

 either kind, however, here is an acknowledgment that the immor- 

 tality of Protozoa is not proved ; that the allegation has no better 

 basis than the failure to observe cessation of fission; and that 

 thus one term of the above antithesis is not a fact, it is only an 

 assumption. 



But now what about the other term of the antithesis the 

 alleged inherent mortality of the somatic cells ? This we shall, I 

 think, find is no more defensible than the other. Such plausi- 

 bility as it possesses disappears when, instead of contemplating 

 the vast assemblage of familiar cases which animals present, we 

 contemplate certain less familiar and unfamiliar cases. By these 

 we are shown that the usual ending of multiplication among so- 

 matic cells is due not to an intrinsic cause, but to extrinsic causes. 

 Let us, however, first look at Prof. Weismann's own statements : 



" I have endeavored to explain death as the result of restriction in the powers 

 of reproduction possessed by the somatic cells, and I have suggested that such 



* See First Principles, part ii, chap, xxii, Equilibration. 



