Premeioh'c 

 P.M. 



3 



Meiosis 



r 



M, 



Ma 



4, 



Fig. 26. Diagram to explain the course of an ordinary nuclear 

 division and the relation to it of the meiotic divisions. 



The series 1-6 P M represents selected stages, in the order in which they 

 occur naturally, of an ordinary nuclear division before reduction in the 

 number of the chromosomes has occurred. 



The series li-6i M represents the stages which roughly correspond to 

 the premeiotic in the first meiotic (reduction) division. Stages 1 and 2 are 

 practically identical. In 5 the longitudinal fission previously seen in 2. 

 is again clearly visible. 



The series 82-62 (Mg) represents the second meiotic division. It shows 

 the subsequent division of nucleus A (Mi-6i) in the series immediately 

 preceding Ma. The corresponding nucleus, B, in series MI 6, is not shown, 

 but its further division is exactly like that of A. 



When A (or B) in M! 6 proceeds to divide, it does so without going 

 through the stages 1-2, but passes at once into A32. The sides of each 

 loop represent the early longitudinal fission of the previous series now be- 

 coming effective. At 42 the halves are seen in pairs and they separate in 

 5g; in 62 is shown the stage at which the nuclei AiAg are finally going back 

 to a resting condition. 



