240 HABIT AND INTELLIGENCE. [chap. xix. 



fied, similar or homologous edges and angles are modified 

 alike. This last, as has been stated in the chapter on 

 Crystallization, is true not only of modifications that arise 

 spontaneously in the process of crystallization, but of 

 such modifications as are artificially produced by breaking 

 off an edge or an angle. 



In this chapter we have considered only morphological 

 relations within the limits of the species. In the next we 

 are to extend our gaze over a much wider horizon, and 

 to consider the morphological relations between widely 

 separated groups. 



NOTE. 



Approach It has been stated (see p. 231) that metagenesis, like that of the 



to meta- Hvdrozoa, is rare among flowerincr plants. Vallisneria spiralis, 



genesis in -^ ' o o r 



Vallisneria however, a plant which inhabits running streams, presents a case 



spiralis. somewhat similar to that described among the Hydrozoa. The 

 female flowers float on the water, like those of a water-lily : the 

 male flowers are matured below the surface, and when the pollen 

 is ripe they become detached, and float on the surface, where 

 they are carried by the current among the female ones. 



