Ill THE UNICELLULAR AND THE MULTICELLULAR 71 



After he lias stated that his notion of the continuity of the 

 germ-plasm reduces heredity to simple growth, and parallels 

 it with the reproduction of unicellular forms in which the 

 same substance grows on and on, and new individuals are 

 only produced by its division, he continues : " The distinction 

 between the unicellular and the multicellular consists only in 

 this — that in the latter every division of the 'germ-substance' 

 is followed by a process of development which leads to the 

 formation of a multicellular individual. This, then, exceeds in 

 mass by an enormous amount the unused remnant of the 

 germ-plasm, but yet it is only a by-product of the eternal 

 germ-substance, is abandoned to death, must die after a tim.e^ 

 while the germ-substance, under the shelter and nurture of 

 the multicellular body (soma), continues to grow, increases in 

 mass, and produces new germ-cells, which possess the power 

 of forming another generation of bodies (somata), in which the 

 same process again takes place. The germ-plasm may there- 

 fore be conceived under the simile of a long creeping root, 

 from which at intervals separate plants arise, the individuals 

 of the successive generations." 



If the body of the multicellular organism is thus, even 

 according to Weismann's ideas, of secondary importance in 

 comparison with the germ-plasm, if the latter corresponds to 

 the unicellular organism, it follows that the multicellular is 

 just as immortal or mortal as the unicellular. And thus it is 

 impossible to see why, between the germ-plasm of the multi- 

 cellular on the one hand, and that of the unicellular on the 

 other, there should exist this profound difference, that the 

 latter acquire characters during life and transmit them by 

 heredity, the former not, — how the former any more than the 

 latter can nourish itself and cjrow without beinq- influenced in 

 its nature bv its nurture. 



