m] CHROMOSOMES IN MITOSIS 35 



arms may be equal in length, or one may be shorter than 

 the other, giving a hook-shaped form. The characteristic 

 shape is best seen in the equatorial plate and early anaphase 

 stages; in the prophase the bending is often irregular, and 

 at that stage the chromosomes can only be identified by 

 their relative lengths. 



When the chromosomes take up their position in the 

 equatorial plate, their arrangement depends both on their 



/> 



*x 



FIG. 3. Examples of equatorial plates showing charac- 

 teristic arrangement of chromosomes. From PAYNE 

 (1909) and ROBERTSON (1915). Compare also Figs. 

 24, 29 and Pis. XVII, XVIII. 



number and on their shapes. Long, rod-shaped chromo- 

 somes are typically arranged in a radial position, with their 

 inner ends converging in the centre of the equatorial plate, 

 their outer ends towards the circumference. Chromosomes 

 bent into the form of a V have the angle pointing towards 

 the centre and the two arms diverging outwards (cf . Fig. 29, 

 p. 233). Very short rods and nearly spherical chromosomes 

 are commonly arranged in circles, at even distances from one 



32 



