1896.] On Heredity and Bejurt)iat!o)i. 7 



original thesis. 7 Moreover, in an especial short article I have 

 directed attention to the fact that Weismann has not consid- 

 ered the essential issue of the problem. The difficulties 

 pointed out still remain, and, according to my conviction, can- 

 not be removed. Weismann passes these difficulties by and 

 carries out his speculations without first securing a basis for 

 them. His method is illustrated by the following quotation : 

 " I have, perhaps, not to regret that I cannot here discuss the 

 article referred to (Minot's Article in Science, Vol. IV, p. 398) ; 

 nevertheless, almost all objections which are there made to 

 my views are answered in the present paper." (Weismann, 

 Zur Frage nach der Unsterblichkeit der Einzelligen, Biol. 

 Centralbl., IV, 690, Xachschrift). I have studied the paper 

 with conscientious care and cannot admit that the objections 

 have been answered. On the contrary, I maintain now, as 

 formerly, the judgment : " He misses the real problem." 

 For this reason I hold it to be unnecessary to discuss the de- 

 tails of Weisman's exposition, because — if I am right— he has 

 not considered the actual problem of death at all. " He 

 misses the real problem." The following reasoning leads to 

 this decision : Protozoa and Metazoa consist of successive gen- 

 erations of cells ; in the former the cells separate ; in the lat- 

 ter they remain united ; the death of a Protozoa is the anni- 

 hilation of a cell, but the death of a Metazoon is the dissolu- 

 tion of the union of cells. Such a dissolution is the result of 

 time, that is to say, of the period necessary to the natural 

 duration of life, and we call it, therefore, "natural death." 

 Moreover, we know that natural death is brought about by 

 gradual changes in the cells until, at last, certain cells, which 

 are essential to the preservation of the whole, cease their func- 

 tions. Death, therefore, is a consequence of changes which 

 progress slowly through successive generations of cells. These 

 changes cause senescence, the end of which is given by death. 

 If we wish to know whether death, in the sense of natural death, 

 properly so called, occurs in Protozoa or not, we must first pos- 



' Journal of Physiology, XII, and Proc. A. A. A. S., XXXIX, (1890). 



