258 Causes and Course of Organic Evolution 



so far-reaching as to affect the protoplasms of each and cause 

 definite growth of each cellulose tube, a considerable time 

 before these tubes have even met. 



The indicative evidence then at present for the simpler 

 algae is that either the nucleus or the eye-spot when present, or 

 perhaps both, represents the specially attractive substance 

 of the cell. But from the vie\\-point of cell-structure already 

 advocated (p. 130) this means that the chromatin is the special 

 sex-related material. 



If in a few sentences we pursue the same hne of investi- 

 gation further amongst plants and animals, and return later 

 to its more detailed study, it is now accepted by most that as 

 one isogamete cell becomes gradually smaller, through suc- 

 cessive stages (as in Oedogoniiun, Sphceroplea, Volvox, Coleo- 

 chcete, and Char a) up to the minute active spermatozoids of 

 Bryophyta and Pteridophyta, decrease of the male or sperm 

 body occurs, till it consists only of a small refractive mass 

 mainly of nuclear chromatin. Even the cilia, that many have 

 regarded as protoplasmic, seem from the researches of Ikeno, 

 Shaw, Strasburger, and others, to be in large part at least 

 chromatic in origin. 



Again, as we similarly advance from the averagely small 

 swarmspore to the egg of Bryophyta and Pteridophyta, a 

 steady increase in relative bulk of nuclear material takes place, 

 so that the nucleus assumes a striking aspect inside the egg. 

 As in Spirogyra nitida so in each egg-cell a powerful attraction 

 of the spermatozoid toward it is exerted, till fusion of both 

 occurs. Yet that the sperm contributes nearly or quite as 

 much molecular energy, and starts equal stereoenergetic flows 

 of molecules as does the egg chromatin, is shown alike by the 

 balanced embryo, and in time adult plant, that is produced. 

 Moreover the writer's studies on plant hybrids (63) definitely 

 demonstrate that every cell of a hybrid may show the balanced 

 influence of both parents, though reduced each to about half 

 the parental strength. 



We accept it then as fully verified that lines of some kind 

 of attractive energy are set up between the chromatin of com- 



