i 9 o8] GATES— REDUCTION IN OENOTHERA 17 



tudinal split appears in the daughter chromosomes. This split does 

 not stop short of one end, giving a V-shaped body as in many plant 

 chromosomes, but usually passes right through, forming two inde- 

 pendent bodies, which, however, remain paired in the telophase and 

 occupy a great variety of positions in regard to each other. The 

 homotvpic chromosomes thus assume many of the characteristic 

 shapes which are usually observed in the heterotypic chromosomes of 

 other forms, such as X, Y, V, H, etc. The failure of the heterotypic 

 bivalents to form these shapes is due partly to the weaker attraction 

 between the members of a pair, but largely to a difference in their 

 shape, each member of a pair being usually more rounded in the 

 heterotypic and more elongated and rodlike during the stages between 

 the two mitoses. 



The telophase of the heterotypic mitosis is one of the best stages for 

 counting the chromosomes, as they are distributed at equal intervals 

 around the periphery of the nucleus, no two ever being in contact and 

 the halves of each (bivalent) chromosome rarely separating. The 

 chromosomes now evidently repel each other, while the halves of 

 each chromosome attract each other rather strongly. The halves of 

 these bivalent chromosomes are usually short rods, but they may be 

 dumb-bell or hour-glass shaped, or nearly globular, as previously 

 mentioned (12). Sometimes, however, this split fails completely to 

 occur in the anaphase, the daughter chromosomes remaining single 

 and globular or somewhat elongated (fig. 39). These telophase 

 stages and the prophases of the homotvpic mitosis will be taken up 

 in detail in a paper dealing with different forms. These results, 

 therefore, will not be duplicated here, but a brief statement of the 

 events of the second mitosis will be given. 



HOMOTYPIC MITOSIS 



In the telophase of the heterotypic mitosis the nuclei never pass 

 into the resting condition and the chromosomes never lose their 

 identity completely, though they spread out and anastomose with 

 each other more or less. Nucleoli are formed, as previously described 

 (11). These stages between the two mitoses last for some time, but 

 the events of the second mitosis are passed through very quickly. The 

 two homotvpic spindles are formed simultaneously and their axes are 



