286 J. JACKSON CLARKE. 



be strong and sharply defined, and in the young parasite there 

 was a single large nucleolus. Later the outline of the nucleus 

 had become irregular and the nucleoli more numerous. In M. 

 agilis, and in one instance in M. magna, Wolters encountered 

 what he has named the flame-nucleus, a condition in which the 

 nuclear membrane has disappeared, and the nuclear substance 

 is prolonged at various points into the protoplasm of the body 

 of the protozoon. As soon as the nucleolus has broken up into 

 subdivisions the parasites are ripe for conjugation. It was 

 found that after the syzygium was formed the nucleus of each 

 parasite moved to the periphery, became elongated, and soon 

 exhibited a typical nuclear spindle with the chromatin now 

 massed together at the middle of the spindle. The chromo- 

 somes were very small. The division of each nucleus took 

 place, and half of each nucleus was extruded as a polar body. 

 Meanwhile the surfaces by which the parasites adhered to each 

 other became altered in such a way that instead of the 

 sharply marked line of division previously seen throughout a 

 complete series of sections of a syzygium, there was at one part 

 of the applied surfaces a communication through which the two 

 parasites fused together. In each parasite the polar body was 

 extruded on the surface opposite this communication, towards 

 which, after the polar bodies had been formed, the two nuclei 

 moved, and having reached the spot at the same time they 

 fused together. After this a nuclear spindle was to be seen in 

 each half of the syzygium, and could be distinguished, by its 

 position close to the area of communication, from the spindles 

 which were concerned with the formation of the polar bodies. 

 Thus it appeared that the conjoined nuclei had undergone 

 division, and that the daughter nuclei were again subdividing. 

 The resulting two nuclei moved towards the periphery in each 

 half of the syzygium, and there formed two spindles. This 

 AVolters found to be the case in complete series of sections. 

 These spindles were smaller than those of the polar bodies. 

 By repeated subdivision these peripheral spindles and resulting 

 nuclei increased in numbers and became surrounded by proto- 

 plasm constituting the sporogonia, which arranged themselves 



