270 Unifcrsity of Califoniia Publications in ZooJogi/ [Vol.16 



common, after eneystment cysts were found with from one to four 

 nuclei. Occasionally the chromatin looks like a spireme and nucleolus 

 (pi. 21, fig. 86) ; again, the spherical granule has divided and has a 

 central connection with the remaining chromatin in a ring around the 

 connection (pi. 21, fig. 85), resembling a late prophase except that 

 no fibers were present. 



These might be interpreted as an incomplete series of maturation 

 divisions occurring in cysts, if it were not for other facts as follow. 

 Many cysts from many cultures, fixed at intervals during the day. have 

 been examined and no other stages have been found. Chromidia are 

 formed at eneystment and some might perhaps persist. A broken-up 

 condition of chromatin is general and characteristic in old cysts. 

 Where the amoebas of cysts in this condition are induced to come out, 

 no copulation has ever been ob.served. The cysts with more than one 

 nucleus are found in cultures in which the amoebas were multinucleate 

 and so were derived from the ency.stment of multinucleate individuals 

 (pi. 21, fig. 80) and the nuclei are not reduction nuclei. From which 

 it follows that the.se are not maturation stages, but by mere accident 

 resemble them. 



Glaser (1912 6) figures maturation in Amoeba mira. In his 

 plate 7, figures 4ffl, 4&, and 7-13, are amoebas immediately prior to 

 eneystment in which there is heavy peripheral chromatin. Of these, 

 figures 8-11 are division stages in which the karyosome is more or less 

 like a dumb-bell in .shape and has the peripheral chromatin about its 

 two extremities. Except for the la.st-meutioned figures, the stages 

 figured are comparable to chromatin extrusion prior to ency.stment as 

 shown in our plate 21, figures 67, 68, 70, 75 of Xaegleria gruheri. The 

 reduction of Gliiser's thirty-two double chromatin rods, which become 

 sixteen on the spindle, is possibly the parallel of the chromosome for- 

 mation in vegetative mitosis of N. griihrri in which numerous granules 

 assemble to form the eight chromosomes (pi. 20, figs. 41, 56). His 

 early synapsis looks very much like figure 86 of plate 21, which is an 

 old cyst with the karyosome broken up. The fact that there are small 

 spindles in some cysts and large in others, small nuclei in some and 

 large in others, and large nuclei and small spindles in some, does not 

 necessarily signify maturation. In Xaegleria gruheri nuclear size 

 varies decidedly in the vegetative condition (cf. pi. 18, figs. 10, 11) and 

 also in cysts (pi. 20, fig. 64). The presence of five nuclei in one cyst 

 does not necessarily mean that it is a stage in maturation. The unlike 

 karyosomes (Glaser, 1912 h, pi. 8, fig. 34) may merely be a condition 



