Vol. 33 



BULLETIN 



No 5. 



OF THE 



TORREY BOTANICAL CLUB 



MAY, 1906 



A study of synapsis and reduction 



Ira D. Cardiff 



(with plates 12-15) 



From the standpoint of heredity the critical stages in an or- 

 ganism are at fertilization and reduction. That in fertilization there 



t 



is an approximate doubling of the number of chromosomes, half 

 of which were contributed by each gamete, there is no longer any 

 doubt. That this number must be reduced at some time previous 

 to the next union of gametes is equally evident. The method by 

 which reduction is accomplished is not so evident, although the 

 researches of the past few years give promise of an ultimate solu- 

 tion of the problem. 



Recent investigations of McClung, Montgomery, Rosenberg, 

 Sutton, Wilson, and others have thrown much light upon the 

 question of the individuality of the chromosomes. The work of 

 these investigators strongly supports the theory that there is a 

 differentiation among the chromosomes. Montgomery ('05) is of 

 the opinion that their individuality is not lost through the growth 

 phase of an organism but that each chromosome of a generation 

 had its predecessor in a preceding generation ; that is, there is no 

 de novo formation at mitosis. Fick ('05), in a recent discussion in 

 which he goes into the whole cytological question in so far as it 

 bears upon the germ cells, opposes this view as a matter of opinion, 

 but offers no additional data upon the subject. The evidence at 

 present is so very strongly in favor of the theory that the individu- 

 ality of the chromosomes is retained throughout the history of the 

 organism that it can well be used as a working hypothesis. 



[The Bulletin for April 1906 (33: 213-270, //. /o, if) was issued 10 My 



1906. ] 



27 1 



