342 THE INDUCTIONS OP BIOLOGY. 



94. But here a difficulty presents itself. These proposi- 

 tions seem to involve the conclusion that self-fertilization is 

 impossible. It apparently follows from them, that a group of 

 physiological units from one part of an organism ought to 

 have no power of altering the state of approaching balance in 

 a group from another part of it. Yet self-fertilization does 

 occur. Though the ovules of one plant are generally fer- 

 tilized by pollen from another plant of the same kind, yet 

 they may be, some of them, fertilized by pollen of the same 

 plant ; and, indeed, there are plants in which self-fertilization 

 is the rule : even provision being in some cases made to pre- 

 vent fertilization by pollen from other individuals. And 

 though, among hermaphrodite animals, self-fertilization is 

 usually negatived by structural or functional arrangements, 

 yet in certain Entozoa there appear to be special provisions 

 by which the sperm-cells and the germ-cells of the same indi- 

 vidual may be united, when not previously united with those 

 of another individual. Nay, it has even been shown that in 

 certain Ascidians the contents of oviduct and spermiduct of 

 the same individual produce, when united, fertile ova whence 

 evolve perfect individuals. Certainly, at first sight, these 

 facts do not consist with the above supposition. Neverthe- 

 less there is something like a solution. 



In the last chapter, when considering the variations caused 

 in offspring from uniting elements representing unlike 

 parental constitutions, it was pointed out that in an unfolding 

 organism, composed of slightly-different physiological units 

 derived from slightly-different parents, there cannot be main- 

 tained an even distribution of the two orders of units. We 

 saw that the instability of the homogeneous negatives the 

 uniform blending of them ; and that, by the process of differ- 

 entiation and integration, they must be more or less separated ; 

 so that in one part of the body the influence of one parent 

 will predominate, and in another part of the body the influe- 

 ence of the other parent: an inference which harmonizes 

 with daily observation. We also saw that the sperm-cells or 



