436 KINSHIP AND ADAPTATION 



tracing of kinship that it is often obscured l)y the workings of other 

 laws. Recapitulation is understood to be a consequence of the 

 general rule that organisms inherit as far as possible all the pecul- 

 iarities of their ancestors, and so have similar young stages; but 

 new features may appear even in the young which can be inherited 

 only by obscuring or obliterating the old. 



Sometimes bluebell flowers are found having distinct petals, 

 and so resembling what evolutionists suppose to have been the 

 remote ancestral form. Such exceptional adult forms resembling 

 younger stages or presenting features which on other evidence may 

 be regarded as ancestral, are classed as reversions. It is a common 

 experience of breeders to ol^serve some striking peculiarity of an 

 animal or plant disappear in the first generation of offspring and 

 then reappear in those of the second or some subsequent generation. 

 This reappearance is called atavism ' and seems to differ from re- 

 version only in the remoteness of the ancestor to which the descend- 

 ant reverts. Reversions are of interest to the evolutionist as often 

 affording confirmation of views of kinship otherwise made probable. 

 It should be borne in mind, however, that many abnormalities have 

 no claim to be called reversions. 



Another clue to kinship is found in rudimentary organs, 

 such for example as the imperfectly developed ovules of 

 anemonies. The presence of these presumably useless organs 

 may be explained bj' supposing them to be vestiges inherited 

 from an ancestor which had in each ovary several perfect 

 ovules; and when we find such a plant as the marsh-marigold, 

 very like an anemony except for having perfect ovules in 

 place of the rudimentary ones, our conviction that these 

 plants are closely akin is much strengthened. Furthermore, 

 these rudimentary ovules in anemonies serve to bridge the 

 gulf which separates those members of the crowfoot family 

 which have several ovules from those wdiich have only a 

 single one in each ovary, for they seem to preserve a stage 

 in the process by which several ovules were crowded out. 



In the light of what we lia'\-c learned of the general principles of 

 evolution let us now re-examine the members of the Ranunculaccee 

 represented in the family chain on page 353, and see to what more 

 definite conceptions they may lead us. The family chain diagram 

 may be taken to represent a toj) view of the branches of a family 

 tree, the rectangles standing for living genera, and the links connect- 

 ing them for the forks of extinct or buried branches. This same 

 family tree viewed from the side, the branches being swung round 

 ' At'a-vism < L. aluviix, a great-grandfather's grandfather. 



