﻿1903] BEHAVIOR OF THE CHROMOSOMES 2^^ 



Fig. I. a, by c, and ^represent four chromosomes shortly after the cross 

 I segmentation of the spirem ; in a the daughter segments are somewhat 



closely applied and twisted upon each other; in b the ends show a tendency 

 to separate and diverge ; and in c the segments are almost separate save at 

 one end; ^ is a case in which the chromosome is somewhat bent and the 



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segments are in close contact near the middle. X about 1750. 



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Fig. 2. Various forms of chromosomes observed in the nuclear plate: a, 

 the chromosome is fastened to the spindle at the end, and consists of two rod- 

 shaped segments twisted upon each; b, the two segments which adhere at 

 both ends bend out at the middle to form the ring-shaped chromosome ; such 

 chromosomes are generally placed tangentially upon or within the spindle ; 

 c to h represent several other forms of chromosomes commonly met with ; 

 the bundl'e of fibers shows the method of attachment to the spindle; / is an 

 X-shaped chromosome, although in this form of chromosome the ends may 

 diverge more; h is a typical Y-shaped chromosome, a and b, X 17S01 ^ to 

 A, X 1500. 



Fig. 3. A nearly mature spindle ; the chromosomes are being arranged in 



the nuclear plate. X 1500. 



Fig. 4, A mature spindle showing only three chromosomes. X 1500. 



Fig. 5. Chromosomes in metakinesis; each daughter chromosome con- 

 sists of two granddaughter segments as the result of the second longitudinal 

 splitting; the granddaughter segments adhere at the ends to which the 

 bundle of spindle fibers is fastened, while the opposite ends diverge to form 

 the familiar V-shaped figures; the chromosomes in this figure are all fast- 

 ened to the spindle by the ends. X 1500. 



Fig. 6. Two chromosomes from a karyokinetic figure in the same stage 

 ^^fiS'-S f the chromosome at the right was fastened endwise to the spindle, 

 and consequently the retreating pairs appear as two rods lying side by side 

 or as V-like figures; the chromosome at the left was in the form of either a 

 complete open or an incomplete ring: the daughter segments are therefore 

 somewhat U- or V-shaped with one limb of the U, or V a little longer than 

 the other; the V-shape here is due to a bending; each U or V is double as 

 a result of the second longitudinal fission. X 1750. 



Fig. 7. Median section of an entire pollen mother-cell. The chromosomes 

 are in the anaphase ; the granddaughter segments form V's or pairs of nearly 

 parallel rods. X 1500. 



Fig. 8. The same stage as the preceding ; the daughter chromosomes on 

 the right and left consist each of two U- or hook-shaped granddaughter seg- 

 Txients owing this form to a bending; the granddaughter segments of those 

 in the middle are contiguous rods slightly bent or hooked at one end. 

 X 1500. 



Fig. 9. Five daughter chromosomes nearly at the poles; the grand- 

 daughter segments which are at a slight distance apart are connected by fine 

 threads. X 1750. 



