330 SYDNl^Y J. HICKSON. 



AtteDtion may bei'e be directed to two important points of 

 comparison with ciliate Infusoria. The difference between 

 the migratory or male germ nucleus and the stationary or 

 female germ nucleus is in Dendrocometes reduced to a 

 minimum. It is possible that in all cases one germ nucleus 

 traverses the membrane and the other does not, so that the 

 distinction remains, but the two nuclei are as nearly neuters 

 as can be. In the second place, the fusion of the germ 

 nuclei takes place during a resting and not in a mitotic state. 

 According to the researches of Maupas, Hertwig, and 

 others, the germ nuclei of the ciliate Infusoria fuse when in 

 the form of spindles or mitotic figures. 



Stage G (PL 17, fig. 11). — One of the cleavage nuclei 

 passes into each of the conjugating individuals and prepares 

 to divide again by mitosis. The early stages of this division 

 probably occur very soon after the fusion of the germ nuclei, 

 as the figures may be seen sometimes quite close to the 

 membrane (cf. PL 18, fig. 13). This stage may be dis- 

 tinguished from Stage D, which it somewhat resembles, by 

 the fact that the axes of the spindles are not parallel. 



Stage H (PL 17, fig. 12). — The cleavage nucleus divides 

 into two nuclei which take up a position in close proximity to 

 the meganucleus. 



Stage J (PL 18, fig. 1). — The nuclei formed by the division 

 of the cleavage nucleus again divide, and almost immediately 

 one of the four becomes a little larger than the other 

 three. 



Stage K (PL 17, fig. 13).— The largest of the four 

 nuclei of the last stage becomes the new meganucleus, the 

 other three the new micronuclei. There is some evidence to 

 show that occasionally two of the three smaller nuclei again 

 divide in this stage, giving rise to a condition in which there 

 are six nuclei in all, as seen in the preparations from which 

 PL 18, fig. 8, was drawn. In some cases, too, it appears 

 that two nuclei enlarge to give rise to new meganuclear 

 structures, as seen in PL 18, fig. 19. Variations of this 

 kind at these stages have added very much to the ordinary 



