278 THE INDUCTIONS OF BIOLOGY. 



brium. ITence, a group of physiological units cast off from it, 

 will not be wholly without a tendency to undergo the struc- 

 tural re-arrangements which we call development ; but will 

 have this tendenojr unduly restrained by partially-balanced 

 polarities. In the second place, undue restraint of the phy- 

 siological units, while it renders them as wholes less-easily 

 altered in their relative positions by incident forces, thereby 

 also renders them more liable to be individually decomposed 

 by incident forces : the same thermal undulations which, if 

 the physiological units are comparatively free, will aid their 

 re-arrangement by giving them still greater freedom, will, if 

 they are comparatively fixed, begin to change the' arrange- 

 ments of their components — will decompose them. In the 

 third place, their decomposition will be prevented as well as 

 their re-distribution facilitated, by such disturbance of their 

 polarities as we have seen must result froift mixing with them 

 the slightly-unlike units of another organism. 



And now. let us test this hypothesis, by seeing what power 

 it gives us of interpreting established inductions. 



§ 93. The majority of plants being hermaphrodites, it has, 

 until quite recently, been supposed that the ovules of each 

 flower are fertilized by pollen from the anthers of the same 

 flower. Mr Darwin, however, has shown that the arrange- 

 ments are generally such as to prevent this : either the ovules 

 and the pollen are not ripe simultaneously, or obstacles pre- 

 vent access of the one to the other. At the same time, he has 

 shown that there exist arrangements, often of a remarkable 

 kind, which facilitate the transfer of pollen by insects from the 

 stamens of one flower to the pistil of another. Simi- 



larly, it has been found that among the lower animals, herma- 

 phrodism does not usually involve the production of fertile 

 germs, by the union of sperm-cells and germ-cells developed 

 in the same individual ; but that the reproductive centres of 

 one individual are united with those of another, to produce 

 fertile germs. Either, as in the Pyrosoma, the Perophora, aiid 



