62 GENETICS IN RELATION TO AGRICULTURE 
tion figure shown at F, the significant feature of which is the fact that each 
of the daughter nuclei resulting from this division receives only two 
chromosomes instead of the four which the original cell at A contained. 
Since the original cell contained one pair of larger and one pair of smaller 
chromosomes, the daughter cells which are formed each receive one larger 
and one smaller chromosome. 
Cytological investigation is not yet in agreement as to the interpre- 
tation of synapsis especially as to the manner in which the phenomena 
therein concerned are connected with preceding mitotic divisions. Con- 
sidering certain cytological investigations and the results of research in 
Fic. 29.—The reduction division as represented for a species whose diploid number is 
four. A, ‘‘Resting’’ nucleus’ of a primary germ cell. B, Formaton of paired threads of 
chromomeres. C, Conjugation of homologous chromosomes (synapsis). D, Loosening 
of thesynaptic knot. #, Condensation of the chromosomes and disappearance of the nuclear 
membrane. F, Homologous chromosomes about to pass to opposite poles, thus giving each 
secondary germ cell a member of each pair and one-half the somatic number. 
heredity together, it appears that the threads which pair in stage B rep- 
resent pairs of chromosomes with homologous chromomeres occupying 
corresponding positions along their entire length. Likewise the contrac- 
tion stage at C is taken to represent a conjugation of the members of pairs 
of chromosomes which later again separate. Other cytological evidence 
indicates that in some forms the conjugation of pairs of homologous chro- 
mosomes is brought about in another way. However, the essential 
fact is the same in either case. In the reduction figure the members of 
each pair of chromosomes are distributed to the opposite poles of the 
spindle so that the daughter nuclei received only one member of each pair. 
The significance of synapsis lies in the conjugation of homologous 
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