232 HABIT AND INTELLIGENCE. [chap. 



rative products. Siicli detached freely-swimming flowers 

 of the Hydrozoa, as they may be called without metaphor, 

 Medusse. are kaown as Medusse, or jelly-fish : ^ but it is a most 

 important fact, to which we shall have to return again, 

 that there are Medusae which have not this origin. It will 

 appear at least probable, after what has been said, that the 

 freely-swimming MedusES which are detached from some 

 Hydrozoa are homologous with the flower-like organs that 

 remain permanently attached to others : and what makes 

 this probability a certainty is, that both have been ob- 

 served in the same species. The reproductive organs in 

 the same species have been observed in some cases to 

 break off and swim away, while in other cases they grow, 

 mature their products, and die like a flower, without quit- 

 ting the parent stock. A clearer case could not be ima- 

 gined of gradation between the production of a distinct 

 organ, and the production of a distinct organism : for, 

 according to any common and obvious use of words, the 

 flower-like body is only an organ if it matures its products 

 while in connexion with its parent organism, but is a 

 distinct organism if it is detached ; and yet the fact that 

 the two cases occur in the same species conclusively proves 

 that they cannot be fundamentally distinct. 

 In -what I have said that metagenesis does not usually occur among 



genesis flowering plants. But if we are to regard, not the tree, but 

 occurs in ^j^g product of each bud, as an individual, then metagenesis 



flowering -^ . . 



plants. takes place in all trees whatever : the leaf-bearing branches 

 give origin to flower-buds by non-sexual generation, and the 

 flowers give origin by sexual generation to new leaf-bearing 

 buds, which are developed out of their seeds. 



Among the homological relations within the limits of 

 the same species, there are many facts that cannot be 

 accounted for by the principle of the adaptation o 

 structures and functions to each other. To use a 

 concise technical mode of expression ; there are many 

 correlations which are not adaptations. Thus the flower- 

 like generative organs of the Hydrozoa are essentially 



1 It ought perhaps to be mentioned that Thalassicollidae is not Greek for 

 jelly-fish. 



