202 THE SCIENCE OF BIOLOGY 



genesis, stimulation with a particular compound in an 

 extreme state of dilution keeps the egg alive, by causing it to 

 develop. 14 If so small a difference determines life or death 

 for the germ-cell, it may be argued that the senile changes 

 of body-cells are the result of conditions that may some 

 day be comprehended. Is it only a dream to hope that 

 biological science will eventually so analyze the conditions 

 of bodily death and germinal immortality that death, as a 

 natural process, may be postponed if not eliminated? 15 

 Genetics and Cytology: Twentieth century study of 

 evolutionary problems has come to be known as the science 

 of Genetics. Investigation of the origin of species has 

 passed beyond the stage where it is wholly observational. 

 Knowledge of heredity and variation, acquired during the 

 past thirty years, has brought the problem well within the 

 scope of experimentation. The experimental method has 

 been established in this branch of zoological study, although 

 its application has not yet produced results which have led 

 to agreement regarding the causal factors hi evolution. Our 

 earlier contention that evolutionary problems are, in their 



14 The eggs of the marine worm, Thalassema melita, may be caused to develop 

 by artificial parthenogenesis after an immersion for 5 minutes in a solution 



M 



containing 17 cc. of JQ HC1 + 85 cc. of sea-water. This is the equivalent of a 



solution of about .0608% of actual hydrochloric acid. Lefevre, George, 

 "Artificial Parthenogenesis in Thalassema Melita," Jour. Exp. ZooL, Vol. IV, 

 No. 1, 1907. 



16 E. Metchnikoff has discussed at length what science can do to alleviate 

 such disharmonies of the human constitution as the evils of old age and the 

 fear of death, in his book, "The Nature of Man." (Translation edited by 

 P. C. Mitchell, 1903.) Metchnikoff's later theories, concerning the prolonga- 

 tion of human life, through the better adjustment of the physiology of nutri- 

 tion ("The Prolongation of Life," 1908), seem hardly tenable at the present 

 time. But his formulation of this very human problem illustrates the practical 

 answers proposed by science to a group of questions, which, in the past, have 

 been answered only by the metaphysics of religion and philosophy. 



More concrete aspects of the problem of death are briefly summarized by: 

 Jennings, H. S., "Age, Death, and Conjugation in the Light of Work on the 

 Lower Organisms," Popular Science Monthly, June, 1912; and Loeb, Jacques, 

 "Natural Death and the Duration of Life," Scientific Monthly, Dec., 1919. 



