116 president's address — SECTION D. 



adjusted and equilibrated, i.e.,ot two sets of vibrations of different 

 velocities and different amplitudes. This is pure hypothesis, but it 

 goes in the direction towards which the tide of opinion is strongly 

 setting — the correlation of lite energy with those which work 

 physical results only. 



As though springing from the same root stock in the mind, the 

 t-ndn ideas of life and death rise so constantly together that to 

 regard the one and neglect the other would be. in the language of 

 the chemist, to leave a bond unsatisfied ; but Avhat can even a 

 biologist have to say of death more than that it is the universal 

 bourne ? He may, indeed, discredit the ordinary notion which by 

 ei-ecting metaphors into facts succeeds in evolving a positive out of 

 a negative, and creates for itself death as a real presence. He may, 

 at the same time, guard against hasty conclusions in cases where 

 the occui'rence of death is liable to be affirmed on insufficient 

 grounds, by defining it as the absolute loss of the power of evincing 

 the phenomena of cell life; but what then? Death comes to all, 

 and there an end. All that lives dies is the verdict of universal 

 experience. But many biologists are not so sure as once they 

 were that death does come to all of necessity, that individual life 

 must from its very nature and work come to a stop Ground for 

 asserting that some organisms are potentially immortal has been 

 found in the leading feature of the life-history of amoeba and those 

 other monoplastids that propagate by fission of the body into 

 equal parts. Apparently' no valid argument can be adduced 

 against the conclusion that the mature cell undergoing fission does 

 not die. As a unit of life it disappears, but surely it is an abuse 

 of terms to call that death which leaves nothing to show that life 

 has ceased. But though in attaining the end of its existence the 

 cell has acquired immortality, it does not follow from this that 

 prior to maturity it has no inherent tendency to die. There is 

 little doubt that in the higher organisms normal death ensues from 

 the excess of cell waste over cell production, and that this again 

 is the necessary result of the cells being too hardly worked. Cells, 

 like citizens of a commonwealth, have a double duty lo perform — 

 to feed and reproduce themselves, and to discharge whatever 

 fimctions are committed to them for the benefit of the community. 

 In proportion as these latter are more distinctly specified the 

 ability of the cells commissioned to execute them to effect growth 

 and reproduction is diminished because a portion of the energy 

 which should have been expended on self-maintenance is diverted 

 from it, and the more excellent the work performed as a con- 

 sequence of the division of labor the less aptness of the workers 

 to provide for their own wants. All this is obvious enough in its 

 application to many-celled organisms. But it is claimed that in 

 imi-cellular organisms, whose parts are not distinguishable one from 

 another, there is no division of labor; it is the whole cf the cell 

 which reproduces, assimilates, excretes, and so forth. I must 



