sis. But agamo-genesis is not habitual in organisms of very simple structure, which exhibit the first steps in evolution, and in which the absence of highly-specialized tissues shows that integration still possesses its full intensity, and is far removed from equilibrium. Besides, those more complex organisms which exhibit the phenomenon of agamo-genesis, from time to time reproduce by way of gamo-genesis. After a series of agamic generations, the units of the organism will find themselves in an attitude approaching that of mutual equilibrium. The groups of units emitted as germs will no longer be able to assume arrangements which shall give them the form proper to their species, and agamo-genesis will be impossible, or very difficult. The series would come to an end did not sexual generation intervene periodically, restoring a state of instability, which gives back to the organism the power of evolution. Another conclusion, which at first sight appears to contradict the facts, is this, that an organism needs, in order to reproduction, the concurrence of another organism differing slightly from it. This is true of the higher organisms; but lower down in the animal scale, and in most phanerogamous plants, hermaphrodism is apparently the rule. But, not to speak of the fact that most frequently fecundation takes place in monœcious organisms by the intervention of another individual, so that such authors as Huxley and Darwin regard this intervention as the law of reproduction, the hypothesis which we maintain affords an explanation of hermaphrodism in those exceptional cases where it appears to exist beyond question. On the same principles which account for the variable results of the union of near kindred, we can understand how, in the case of hermaphrodites, there may exist simultaneously groups of physiological units coming from each parent, keeping their proper tendencies, which find only partial equilibrium, permitting one or other side to be in excess, and there undergoing the operation of segregation, which produces groups so differentiated that fruitful germs result from their mixture.
Considered in the light of this hypothesis, generation appears as a fact of disaggregation, occurring in an organism in process of equilibration: as a fact of disaggregation, which ever renews the evolution of the species, and which retards its equilibrium by multiplying the conditions under which the species may, under the influence of the incident forces of the environment, undergo a more perfect elaboration, the result of which shall be a better adaptation of the organism to its surroundings. Generation is in fact antagonistic to equilibrium, but this antagonism is only temporary, and causes the organic evolution to obey the law of universal rhythm.
[To be continued.]
