Varietäten. Descendenz, Hybriden. 499 



series ot" generations. Recapitulation is the foUowing over of the 

 ancestral paths of descent in each generation. Otherwise expressed, 

 recapitulation is a temporary or partial expression of a primitive 

 character, whilc reversion is the expression of a character which is 

 usually transmitted in latent form without Coming into expression 

 at all. "Reversion and recapitulation have no limit in years or in 

 numbers ol generations. They give us a vivid indication of the all- 

 embracing, all-enduring power of transmission." 



Reversions are often considered to be rare exceptional pheno- 

 mena but as a matter of fact reversions are frequently as definite 

 and uniform as other processes of descent. For example; the hybrids 

 between the Kekchi cotton of Guatemala and the Sea Island 

 or Egyptian cottons show as one of their most constant characters 

 a dense coat of bluish green fuzz covering seeds underneath the 

 long white lint. Yet neither parent of such hybrids shows any such 

 green fuzz. If the lint is removed from the seeds of Kekchi cotton 

 they are left covered with dense white fuzz, while seeds of Sea 

 Island and Egyptian cottons are left black and naked after the 

 lint has been removed. 



Many varieties of cottons, especially wild or unimproved varie- 

 ties do show such green fuzz and it probably represents an ancestral 

 character from which both of the parental types have diverged, 

 Curiously enough, no wild types of cotton are known that have 

 white fuzz on the seeds like the Kekchi and American Upland types. 



The reappearance of the ancestral green-fuzz character is not 

 permanent; Kekchi-Sea Island or Kekchi-Egyptian hybrids show 

 Wide diversity in the second generation there being many combina- 

 tions of the parental characters and intergradations between them. 

 The green fuzz sometimes reappears to some extent in the second 

 generation and even in the third generation of the hybrids. 



The differences between the first and second generations oi 

 hybrids are shown to depend on the very different nature of the 

 cellorganization in the two cases. During the first generation only 

 one of the two critical periods of adjustment of the internal relations 

 governing the expression of characters has been passed — the proto- 

 plasts and the nuclei of the two germ cells have fused but the 

 vitally important chromosomes remain distinct until the close of 

 the first generation when the process of conjugation is brought to a 

 close by mitapsis which brings about the second adjustment of ex- 

 pression relations. The first generation of the hybrid is formed 

 during the preliminary stage of conjugation and the temporary 

 expression of an ancestral character may not differ essentially from 

 the phenomena of recapitulation in which a temporary expression 

 of an ancestral character takes place normally. 



The behaviour of the green-fuzz character may be described as 

 the converse of typical cases of MendeJism, for a character very 

 prominent in the first generation tends to disappear in the later 

 generations, whereas, if the green-fuzz character behaved in Men- 

 delian manner half of the second generation would have green 

 seeds. On the Mendelian theory the germ cells formed by the first 

 generation hybrids would carr}^ either the black-seeded Egyptian 

 or Sea Island characters or the white seeded Kekchi characters. 

 Half these germ cells would conjugate with others of similar nature 

 and give rise to equal proportions of white and black seeds while 

 half would conjugate with unlike cells and reproduce green-seeded 

 plants. As a matter of fact nothing of the kind occurs. The proba- 



