SUTTON 



In a recent announcement of 

 some results of c critical study of the 

 chromosomes in the various cell-gen- 

 erations of Brachystola ^ the author 

 briefly called attention to a possible 

 relation between the phenomena there 

 described and certain conclusions first 

 drawn from observations on plant hy- 

 brids by Gregor Mendel - in 1865, and 

 recently confirmed by a number of 

 able investigators. Further attention 

 has already been called to the theoret- 

 ical aspects of the subject in a brief 

 communication by Professor E. B. 

 Wilson.^ The present paper is devoted 

 to a more detailed discussion of these 

 aspects, the speculative character of 

 which may be justified by the attempt 

 to indicate certain lines of work calcu- 

 lated to test the validity of the conclu- 

 sions drawn. The general conceptions 

 here advanced were evolved purely 

 from cytological data, before the au- 

 thor had knowledge of the Mendelian 

 principles, and are now presented as 

 the contribution of a cytologist who 

 can make no pretensions to complete 

 familiarity with the results of experi- 

 mental studies on heredity. As will 

 appear hereafter, they completely sat- 

 isfy the conditions in typical Mende- 

 lian cases, and it seems that many of 

 the known deviations from the Men- 

 delian type may be explained by easily 

 conceivable variations from the nor- 

 mal chromosomic processes. 



It has long been admitted that we 



1 Sutton, Walter S., "On the Morphology 

 of the Chromosome Group in Brachystola 

 magna," Biol. Bull, IV., 1, 1902. 



2 Mendel, Gregor Johann, "Versuche iiber 

 Pflanzen-Hybriden," Verb, naturf. Vers, in 

 BrUnn IV., and in Osterwald's Klassiker der 

 exakten Wissevschajt. English translation in 

 ]oiirn. Roy. Hon. Soc, XXVI., 1901. Later 

 reprinted with modifications and corrections 

 in Bateson's "Mendel's Principles of Hered- 

 ity," Cambridge, 1902, p. 40. 



3 Wilson, E. B., "Mendel's Principles of 

 Heredity and the Maturation of the Gemi- 

 Cells," Science, XVI., 416. 



must look to the organization of the 

 germ-cells for the ultimate determina- 

 tion of hereditary phenomena. Mendel 

 fully appreciated this fact and even 

 instituted special experiments to de- 

 termine the nature of that organiza- 

 tion. From them he drew the brilliant 

 conclusion that, while, in the organism, 

 maternal and paternal potentialities are 

 present in the field of each character, 

 the germ-cells in respect to each char- 

 acter are pure. Little was then known 

 of the nature of cell-division, and 

 Mendel attempted no comparisons in 

 that direction; but to those who in re- 

 cent years have revived and extended 

 his results the probability of a relation 

 between cell-organization and cell- 

 division has repeatedly occurred. Bate- 

 son ^ clearly states his impression in 

 this regard in the following words: "It 

 is impossible to be presented with the 

 fact that in Mendelian cases the cross- 

 bred produces on an average equal 

 numbers of gametes of each kind, that 

 is to say, a symmetrical result, without 

 suspecting that this fact must corre- 

 spond with some symmetrical figure 

 of distribution of the gametes in the 

 cell divisions by which they are pro- 

 duced." 



Nearly a year ago it became appar- 

 ent to the author that the high degree 

 of organization in the chromosome- 

 group of the germ-cells as shown in 

 Brachystola could scarcely be without 

 definite significance in inheritance, for, 

 as shown in the paper ^ already re- 

 ferred to, it had appeared that: 



■ 1. The chromosome group of the 

 presynaptic germ-cells is made up of 

 two equivalent chromosome-series, 

 and that strong ground exists for the 

 conclusion that one of these is paternal 

 and the other maternal. 



■» Bateson, W., "Mendel's Principles of 

 Heredity," Cambridge, 1902, p. 30. 

 ^ Sutton, W. S., loc. cit. 



