362 THE INDUCTIONS OF BIOLOGY. 



hindermost produced a head, the anterior piece developed an 

 anus, and the middle portion formed both a head and a tail " 

 we are not furnished with an explanation by the hypothesis 

 of gemmules or by the hypothesis of determinants; for we 

 cannot arbitrarily assume that wherever a missing organ has 

 to be produced there exists the needful supply of gemmules 

 or of determinants representing that organ. The hypothesis 

 that physiological units have everywhere a proclivity towards 

 the organic form of the species, appears more congruous with 

 the facts; but even this does not cover the cases in which a 

 new worm grows from a lateral bud. The tendency to com- 

 plete the individual structure might be expected rather to 

 restrain this breaking of the lines of complete structure. 



Still less explicable in any way thus far proposed are 

 certain remedial actions seen in animals. An example of 

 them was furnished in § 67, where " false joints " were de- 

 scribed — joints formed at places where the ends of a broken 

 bone, failing to unite, remain moveable one upon the other. 

 According to the character of the habitual motions there 

 results a rudely formed hinge-joint or a ball-and-socket joint, 

 either having the various constituent parts — periosteum, 

 fibrous tissue, capsule, ligaments. Now Mr. Darwin's hypo- 

 thesis, contemplating only normal structures, fails to account 

 for this formation of an abnormal structure. Neither can 

 we ascribe this local development to determinants: there 

 were no appropriate ones in the germ-plasm, since no such 

 structure was provided for. Nor does the hypothesis of 

 physiological units, as presented in preceding chapters, yield 

 an interpretation. These could have no other tendency than 

 to restore the normal form of the limb, and might be expected 

 to oppose the genesis of these new parts. 



Thus we have to seek, if not another hypothesis, then some 

 such qualification of an existing hypothesis as will harmonize 

 it with various exceptional phenomena. 



§ 97 d. In Part II of the Principles of Sociology, published 



