i9o8] YAMANOUCHI—SPOROGENESIS IN XEPHRODIUM 13 



chromosomes begin to separate; some of them, on the way toward 

 the pole, show a V-shape, the angle being directed toward the i>ole. 

 This does not seem to have resulted from the bending of one daughter 

 chromosome, because it always remains straight after separation; 

 hence the V-shape may be regarded as resulting from a new longitudi- 

 nal fission of the daughter chromosome, providing for the two grand- 

 daughter chromosomes of the second division. This longitudinal 

 fission occurs only at the end of the chromosome directed toward the 

 equatorial region, without proceeding to the other end. The two arras 

 of the V come into contact again as the daughter chromosome reaches 



the pole. 



iter chromosomes pass to the poles 



simultaneously, but there were observed some exceptional cases where 

 some were much delayed {figs. 31, 32); and rarely the irregularity 

 is so extreme that tardy chromosomes are left behind, while their 

 associates are already in an aggregated condition at the pole 



(fig- 34) ■ 



Reconstruction of the daughter nuclei.— TVTien the group 



As a rule, the sets of daug 



o 



chromosomes reaches the pole, each chromosome 



time 



omes from the polar view {fig. 35). Then the vacuolizat 

 begins {fig. 36). There is a certain point of 



difference 



detail between this process and that described in the reconstruction 

 of daughter nuclei in vegetative mitosis ; the polar ends of the daughter 

 chromosomes do not seem to be dra\\-n together so as to give a concave 

 form, but begin to be vacuolized at once, while in a state of loose 

 association. The vacuolization is prominent along the line of the 

 longitudinal fission of the daughter chromosomes, a line which became 

 obliterated \\1ien the chromosomes reached the pole. After the^ for- 

 mation of the nuclear membrane it is not impossible to recognize a 

 certam part of the chromatin substance as representing a certain 

 chromosome {fig. 38); in other words, the vacuolization process in 

 the telophase of the heterotypic mitosis does not cause the chromosomes 

 to return into the ragged chromatin reticulum from which they are 

 formed, but the reconstruction stops before the individual outline of 

 the main body of the chromosome is lost entirely. Therefore, the 

 daughter nucleus does not pass into the resting stage with ragged 



