PLANT HYBRIDIZATION BEFORE MENDEL 203 



accordingly is entire in respect to its idioplasmic content, and is 

 idioplasmatically capacitated to become the germ of a new indi- 

 vidual, (p. 531.) 



The evolution process, from the standpoint of the idioplasm, 

 is depicted by Nageli in the following manner : 



"The idioplasm through accretion [mit der Zunahme] steadily changes 

 its configuration in the successive ontogenies, but relatively slowly ; so that 

 from the embryo of one generation to the embryo of the next genera- 

 tion it makes a small amount of progress. The summation of these 

 progress-differentials through a whole line of descent represents the 

 genetic history of an organism, since the latter through its idioplasm 

 alone holds together in unbroken continuity with the unicellular be- 

 ginning of the stock." (p. 532.) 



"since further, in embryo-formation, the new ontogeny begins as a 

 unicellular individual, so that the Anlagen of the idioplasm come into 

 development which have arisen in the unicellular ancestor, and simi- 

 larly the successively following development of the Anlagen which have 

 their origin in their analogous ancestors, the two cooperating causes, the 

 phylogenetic configuration of the idioplasm successively following, and 

 the developmental stages of the individual conditioned by these, have, 

 as a necessary consequence, that the ontogeny is the recapitulation of 

 the phylogeny." (p. 533.) 



In the idioplasm of an embryo, the micellar rows of Anlagen 

 from the respective parents may in some cases, Nageli holds, have 

 a medium composition, due apparently to the merging of the 

 micellar rows of the two parents. In such cases, intermediate 

 characters will develop. Or, on the other hand, 



"The paternal and maternal rows lie unaltered in the idioplasm of the 

 child, and in different grouping in relation to one another, and bring 

 about in the organism the characters from the two sides, either unmodi- 

 fied beside one another, or only one of the parental characters, while the 

 other remains latent." (p. 534.) 



The relative development or latency of the inherited Anlagen 

 in the child determines the degree of resemblance to the one or 

 the other parent. The theory of descent, then, is concisely stated 

 by Nageli as follows : 



"since from one ontogeny to the next following, idioplasm alone 

 is carried over, therefore the phylogenetic development consists only 

 of the continuous formation of the idioplasm, and the entire pedigree, 

 from the primordial drop of plasma to the now living organism (plant 

 or animal), is really nothing else than an individual consisting of idio- 

 plasm, which in every ontogeny, forms a new individual body corre- 

 sponding to its progress." (p. 541.) 



"of heredity as a specific phenomenon, if we hold the internal essence 

 of the organisms in view, there can really be no discussion, since the 



