RECAPITULATION AND HEREDITY 



281 



They are very commonly modified to form receptacles for a 

 store of food material for the young plant in the form of 

 starch, as in the peas and beans (compare Fig. 56), and may 

 never even leave the seed-coat or emerge above the ground. 

 In such cases they develop no chlorophyll and differ absolutely 

 from ordinary foliage leaves, without, of course, indicating any 

 ancestral stage through which the latter have passed. Even 

 when they emerge above the ground, as in the beech (Fig. 133), 

 and become green, their form is usually widely different from 

 that of the foliage leaves and 

 appears to have been developed 

 largely in adaptation to the neces- 

 sity for close package within the 

 narrow compass of the seed-coat, 

 the shape of the cotyledons being 

 governed, as Lord Avebury has 

 pointed out, by that of the seed 

 within which, in a dormant condi- 

 tion, they pass most of their lives. 

 In short, the embryological 

 investigation of both animal -and 

 vegetable organisms leaves no 

 doubt as to the general truth FIG. ^133. 

 of the recapitulation hypothesis, 

 and must convince any unbiassed 

 observer that, however much modified it may be by abbrevia- 

 tion and by the superposition of secondary features, the life-history 

 of the individual is essentially a condensed epitome of the 

 ancestral history of the race. The law of recapitulation, indeed, 

 may be regarded simply as a logical extension of the law of 

 heredity, for every organism tends to inherit the characters not 

 only of its immediate progenitors but of all its ancestors, and 

 these characters appear in the individual life-history in the same 

 order as that in which they first appeared in the ancestral 

 history in other words, ontogeny is a repetition of phylogeny 

 and can only be explained in terms of organic evolution. 



Seedling of Beech, 

 showing the Cotyledons. 

 (From Lubbock.) 



