INADEQUACY OF NATURAL SELECTION, ETC. 691 



Dricsch, by separating the first two and the first four segmentation spheres 

 of an EcMnu* ovum, obtained two or four normal plutei, respectively one 

 half and a quarter of the normal size. ... So, also, in the case of 

 Amphioxuft, Wilson obtained a normal, but proportionately diminished 

 embryo with complete nervous system from a separated sphere of a two- 

 or four- or eight celled stage. . . . Gliabry obtained noriral embryos 

 in cases where some of the segmentation-spheres had been artificially de 

 stroyed.&quot; 



These evidences, furnished by independent observers, unite in 

 showing, firstly, that all the multiplying cells of the developing 

 embryo are alike ; and, secondly, that the soma-cells of the adult 

 severally retain, in a latent form, all the powers of the original 

 embryo- cell. If these facts do not disprove absolutely Professor 

 Weismann s hypothesis, we may wonderingly ask what facts would 

 disprove it ? 



Since Hertwig holds that all the cells forming an organism of 

 any species primarily consist of the same components, I at first 

 thought that his hypothesis was identical with my own hypothesis 

 of &quot; physiological units,&quot; or, as 1 would now call them, constitu 

 tional units. It seems otherwise, however ; for he thinks that 

 each cell contains &quot; only those material particles which are bearers 

 of cell-properties,&quot; and that organs &quot; are the functions of cell- 

 complexes.&quot; To this it may be replied that the ability to form 

 the appropriate cell-complexes, itself depends upon the constitu 

 tional units contained in the cells. 



