336 WALTER S. SUTTON. 



in the results obtained by Boveri ' in a study of larva; actually 

 lacking in certain chromosomes of the normal series, which seem 

 to leave no alternative to the conclusion that the chromosomes 

 differ qualitatively and as individuals represent distinct poten- 

 tialities. Accepting this conclusion we should be able to find an 

 exact correspondence between the behavior in inheritance of any 

 chromosome and that of the characters associated with it in the 



organism. 



In regard to the characters, Mendel found that, if a hybrid 

 produced by crossing two individuals differing in a particular 

 character be self-fertilized, the offspring, in most cases, conform 

 to a perfectly definite rule as regards the differential character. 

 Representing the character as seen in one of the original parents 

 by the letter A and that of the other by a, then all the offspring 

 arising by self-fertilization of the hybrid are represented from the 

 standpoint of the given character by the formula A A : 2Aa : aa. 

 that is, one fourth receive only the character of one of the original 

 pure-bred parents, one fourth only that of the other ; while one 

 half the number receive the characters of both original parents and 

 hence present the condition of the hybrid from which they sprang. 



We have not heretofore possessed graphic formulae to express 

 the combinations of chromosomes in similar breeding experi- 

 ments, but it is clear from the data already given that such 

 formulae may now be constructed. The reduced chromosome 

 series in BracJiystola is made up of eleven members, no two of 

 which are exactly of the same size. These I distinguished in my 

 previous paper by the letters A, B, C, . . . K. In the unreduced 

 series there are twenty-two elements 2 which can be seen to make 

 up two series like that of the mature germ-cells, and hence may 

 be designated as A, B, C . . . K -f- A, B, C . . . K. Synapsis results 

 in the union of homologues and the production of a single series 

 of double-elements thus : A A, BB, CC . . . KK, and the reducing 

 division affects the separation of these pairs so that one member 

 of each passes to each of the resulting germ-products. 



1 Boveri, Th., " Ueber Mehrpolige Mitosen als Mittel zur Analyse des Zelikerns," 

 Ver/i. d. Phys.-Med. Ges. zu iriirzbitrg, N. F., Bd. XXXV., 1902. It appears 



from a personal letter that Boveri had noted the correspondence between chromosomic 

 behavior as deducible from his experiments and the results on plant hybrids as indi- 

 cated also in footnote I, /. c. , p. Si. 



2 Disregarding the accessory chromosome which takes no part in synapsis. 



