1904.] MONTGOMERY— CELLULAR BASIS OF HEREDITY. 13 



of the Other (Montgomery, /. c; Sutton, The Chromosomes in 

 Heredity J 1903)- The two that pair are of corresponding vol- 

 ume (as brought out especially by Sutton), and sometimes of cor- 

 responding form (Montgomery, in a paper now in press). Because 

 they are thus similar in volume and form, it is at least possible that 

 they are similar in hereditary value. So Sutton has ably argued 

 that when the two of a pair, a maternal and paternal chromosome 

 of corresponding volume, separate from each other in the reduc- 

 tion division, chromosomes of like hereditary quality become sepa- 

 rated into separate cells, so that no mature germ cell shall contain 

 before fertilization two chromosomes having similar hereditary 

 values. And this is the best reason yet given in explanation of the 

 peculiar reduction division. 



VI. 



Finally, we may ask how far these facts agree with the germ- 

 plasm theory of VVeismann. 



Some eighteen years ago, Carnoy {La cytodierese chez les arthro- 

 podes, 1885) showed, and he was the first to do so, that two kinds 

 of cell division occur, namely, a transverse splitting of the chro- 

 mosomes and a longitudinal splitting. That transverse splittings of 

 chromosomes should occur was directly opposite to the prevalent 

 view of the time, to the effect that only longitudinal divisions take 

 place. Carnoy was far ahead of his day, and while this most im- 

 portant memoir of his then and for years afterwards met with only 

 rather scornful criticism, we must now grant him his proper place as 

 the discoverer of the reduction divisions. 



Weismann, in 1887 {Ueber die Zahl der Richtuiigskorper mid 

 ueber ihre Bedeutung filr die Vererbung), prophesied, clearly with- 

 out knowledge of Carnoy's work, and in conformity with the ideas 

 of Roux (1883, /. c), that in addition to the longitudinal splitting 

 of the chromosomes, the '' hereditary equal division," there would 

 be found to occur in certain generations of the germ cells a 

 * 'hereditary unequal division," either by a transverse division of 

 the chromosomes or by a separation of entire chromosomes from 

 each other. A number of the students of the maturation phe- 

 nomena of the germ cells have empirically demonstrated this. 

 Weismann' s reduction division is the one where entire chromo- 

 somes become separated from each other. Equally, confirmation 

 has been brought of another of his cardinal postulates, the con- 



