DOCTRINE OF ORCJANIC EVOLUTION 435 



having wings and feathers like a bird, but with the toothed 

 jaws and long, jointed tail of a reptile were discovered in 

 rocks of just tlie age required by the theory. 



Such backward reasoning of course yields trustworthy 

 results largelj' in proportion to the fulness of our knowledge 

 regarding all the forms of the group studied, and all stages of 

 their life. The younger stages are especially noteworthy in 

 tracing kinship, for it has been found as a general rule that 

 the earlier the stage at which related organisms are com- 

 pared the closer are the resemblances. We have already seen 

 an example of this rule in our comparison of the development 

 of flowers belonging to the crowfoot and the bluebell types. 

 If we compare such flowers as those in Figs. 298, and 299 I 

 we find that in the earliest stage both have five distinct petals; 

 but while in the rose these petals continue to grow separate, 

 in the oxeye the whole corolla-base soon begins to grow as a 

 continuous ring carrying upward the petal rudiments so that 

 they finally appear as teeth or projections on the margin of a 

 bell. Hence, we may suppose a degree of kinship between 

 the rose and the oxeye, or the flax (Fig. 217 IIj and the blue- 

 bell (Fig. 299 II), which a comparison of their mature flowers 

 would not so clearly reveal, and the fact that the mature 

 corolla of the rose is essentially like the young corolla of the 

 oxeye indicates that the ancestor common to both was more 

 like a rose than an oxeye; or in other words, that the bluebell 

 type of coroHa has been the more highly evolved, while that 

 of flax or rose has more nearly retained the ancestral form. 



Many such facts incline evolutionists to bielieve that the 

 successive stages passed through by an individual in its 

 development correspond more or less closely to the various 

 forms which appeared successiveh' in its line of ancestry. 



The development of an individual organism from egg to adult 

 is termed its ontogeny,^ while the evolution of the group to which it 

 belongs is distinguished by the term phylogeny.- It is commonly 

 accepted as a general rule by evolutionists that ontogeny epitomizes 

 phylogeny, and this is called the law of recapitulation. We shall have 

 occasion, however, to notice in our attempts to apply this law in the 



1 On-tog'en-j- < Gr. otita, things existing; gennao, to produce. 



2 Phy-log'en'-y < Gr. phijlon, a tribe. 



