The karyotypes of the offspring of
Scilla permixta, the II type (2
n=15=
B1B2), were analyzed from the view point of the differentiation or, the evolution of basikaryotype. The B
1 with 8 chromosomes is the most primitive one from which the
B2 with 7 chromosomes seems to be derived by elimination of the S
t3 chromosome. In this form a new sat-chromosome M
t4 originates by translocation of a satellite to the M
4 chromosome. The
B3 seems to be formed from the
B1 by translocation of the S
t3 chromosometo the distal end of the Ma chromosome. Another sat-chromosome M
34 with secondary constriction appeared in this form.
When three different sat-chromosomes are differentiated from the S
t3 sat-chromosome of the
B1, basikaryotypes with two sat-chromosomes such as
B4 and
B5 may be differentiated, and the occurrence of hasikaryotype with threee sat-chromosomes such as
B6 may be expected in-the offspring of the individual no. 1. The process of the differentiation of the basikaryotype started from the
B1, through
B2,
B3,
B4 and
B5 finally to the
B6 is clearly demonstrated: the seven chromosome types in the basis are derived from the eight chromosome type, and two and three sat-chromosome types are derived from one sat-chromosome type.
The present observation of the differentiation of basikaryotypes contributes to the conception of the genome which implies the necessary and well-balanced genes for the viability and is altered in its balance gradually in the process of the evolution.
In conclusion the writer's hearty thanks are due to Prof. Sinoto of the Tokyo Imperial University for his kind advice in the course of this investigation.
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