178 BOTANICAL GAZETTE [march 



resting nucleus of the young antheridium, are not paired, but single. 

 As a consequence, the loops in synapsis are single in nature. An 

 examination of the loops cut transversely during synapsis showed 

 that the arms of the loops are altogether about 64 in number (fig. 21). 

 Finally, both ends of the loops being detached, 64 chromosomes are 

 formed, each pair of which, being derived from two arms of a loop, 

 becomes a pair of bivalent chromosomes. The number of these 

 bivalent chromosomes may be readily counted again in the polar 

 view of the equatorial plate (fig. 25) . When the two halves of a 

 bivalent chromosome begin to separate, the figure (fig. 26) shows 

 the characteristic aspect of the heterotypic mitosis. The two sets of 

 the daughter chromosomes then separate and proceed to the poles of 

 the spindle (figs. 27, 28, 2Q, 30) . The central spindle is of short 

 duration; when the daughter chromosomes aggregate in a mass and 

 organize a new nucleus, the spindle fibers entirely disappear. The 

 centrosomes disappear at the end of telophase. 



The two daughter nuclei, after a short rest, commence the second 

 division, which is simultaneous, the antheridium remaining without 

 much increase in size. In prophase, 32 chromosomes are differ- 

 entiated from the chromatin reticulum, and in the later part of this 

 phase two centrosomes appear (figs. 31, 31a) one after the other; the 

 achromatic spindle is developed in connection with the centrosome 

 and an intranuclear mitotic figure is established (figs. 32, 3 2a )- 

 Metaphase (fig. 32), anaphase (fig. 33), and telophase in the two 

 nuclei proceed simultaneously and finally four nuclei are formed. 



Soon after the telophase, the cytoplasm between the four newly 

 formed nuclei shows a fibrillar arrangement connecting the nuclei, 

 but the display is of short duration and the four nuclei remain either 

 m a group or scattered with no regularity along the longitudinal axis 

 of the antheridium. The second division does not differ much from 

 typical mitosis, except that the nuclear membrane dissolves at an 

 earlier stage in prophase, and that no cell plate is laid down between 

 the daughter nuclei. 



«, • ?!?. f ° Ur nUdei b the anth eridium, after a short rest, begin the 

 third division, which is accompanied by a gradual growth of the cell- 

 ihe third division in each of these four nuclei naturally results « 



34, 34*, 35, 35a, 16, 76a). The eight nuclei give 



(figs 



