1919] Kofai-d-Swczij: Lcidyopsis sphaerica 109 



(pi. 13, figs. 7, 8, 11), gradually assume a V-shaped form, and the 

 cloudy appearance surrounding them disappears, leaving them dis- 

 tinct against a clear background (fig. 16). 



These different phases of nuclear organization are almost identical 

 with those previously described for Trichonympha campanula. There 

 is some suggestion in figure 16 of plate 13 that the chromosomes are 

 arranged in pairs, as in Trichonympha. This point, with an exact 

 count of the number of chromosomes, could not be as clearly made 

 out here as in the other species, owing to the small number of individ- 

 uals under observation. The number of chromosomes seems to be 

 slightly less than that of Tricho-nympha, though this cannot be stated 

 with certainty. In the prophase this seems to be forty-eight (pi. 13, 

 fig. 15), with a reduction to twenty-four in the later stages (pi. 14. 

 figs. 18-22). The process of pseudosynapsis by means of which this 

 reduction takes place, cannot be figured from our material but is 

 evidentlj" similar to the same process in Trichonympha. 



Metaphase: This stage also has been lacking in our material. 

 The appearance of the following anaphase (pi. 14, fig. 17) would 

 suggest in part the probable mode of procedure. In the late prophase 

 the nueleiis had taken its place close against the paradesmose (pi. 13, 

 figs. 15, 16), and elongated until its length is equal to that of the 

 paradesmose. Spindle fibers are formed from the ends of the parades- 

 mose or bases of the centroblepharoplasts, and to these the chromo- 

 somes become attached, with a single fiber from each pole attached to 

 the end of the chromosome lying nearest it. The nuclear membrane 

 remains intact throughout the entire process of mitosis. 



Anaphase : A slight shortening of the spindle fibers assists in the 

 separation of the chromosomes, but apparently this is more dependent 

 upon a lengthening of the entire nucleus in the equatorial plane than 

 upon any other factor. The spindle fibei"s show but little contraction 

 up to the time of their disappearance in the late telophase, and the 

 chromosomes are not drawn to the poles (pi. 14, fig. 23). The nucleus 

 becomes greatly elongated and constricted in the middle until the 

 two halves are connected by a slender line of niiclear material. The 

 paradesmose also increases in length. 



As the chromosomes separate the heterochromosorae may usually 

 be found near the ends of the two groups (pi. 14, fig. 19). As in 

 Trichonympha it is the lagging chromosome and is apparently the last 

 one to divide. In a later stage this assumes a coiled shape preparatory' 

 to the formation of the vesicle by which it is later enclosed (fig. 20). 



