REPRODUCTION 



47 



time, fibers become distinct; two groups of chromosomes move 

 toward the opposite ends and finally divide into two daughter 

 nuclei. In these two cases the nuclear membrane persists. 



In the microsporidian, Thelohania legeri (Fig. 20), the spor- 

 ont nucleus divides mitotically. Formation of spireme and 

 spindle fibers and disappearance of the nuclear membrane are 

 distinctly observable, although whether the chromosomes split 



Fig. 21 Nuclear division in Menoidium incurvum. X about 1400. (After 

 Hall), a, resting phase; b, c, prophase; d, "equatorial plate;" 

 e, f, anaphase; g, telophase. 



or not cannot be made out. In Mastigophora, which possess, as 

 a rule, a blepharoplast from which a flagellum arises and which 

 behaves in a manner somewhat comparable to that of the central 

 granule of Oxnerella or of the centrosome in a metazoan mitosis, 

 the blepharoplast divides and produces a strand between the 

 divided parts in close association with the nucleus. This strand 

 is known as the paradesmose, or centrodesmose (Figs. 21, 22). 

 In several Mastigophora, a clear picture of the metaphase has 

 been observed by numerous investigators. 



