The Message of Science. 69 



hours, because no more time is needed for depositing her 

 eggs. With mammals, on the other hand, years are re- 

 quired for the rearing of offspring sufficient to make good 

 their places in nature. 



(5) With regard to the proximate causes of death, 

 Weismann holds it to be due to the somatic cells losing the 

 power of growth and multiplication after a certain length 

 of time, or a certain number of cell generations. "Length 

 of life in the individual is dependent upon the number of 

 generations of somatic cells, which are able to succeed 

 each other from the original endowment in the ovum." 



(6) As regards heredity and inheritance, Professor 

 Weismann discredits the common opinion that the per- 

 sonal lives, habits and efforts of parents affect the 

 character of their offspring. His theory of a distinct 

 germ-plasm controverts the concept of Darwin that " gem- 

 mules " from all the somatic cells are garnered up in the 

 reproductive cells, and thus reduplicate the parents in 

 their offspring. Nothing of this, from the soma, is con- 

 veyed to the germ-plasm, or affects, save in extreme 

 contingencies, the reproductive cells. 



Like Herbert Spencer, Weismann conceives that life on 

 its lowest plane, unmodified by environment and unor- 

 ganized, e5cists through or by virtue of "physiological 

 units," which he, however, terms hiophors (life-bearers), 

 a conception ■ not unlike that of the plasomes of Briicke,. 

 or the plastidules of Haeckel. In the lowest forms of 



