No. 3-] THE PROTOZOA AND METAZOA. 723 



dinally, i.e., in planes which pass through the secondary or the 

 primary axis. In transverse section the chromosomes are thick, 

 double fibers which tend to converge in the median line and to 

 spread out from here like the ribs of a fan (Figs. 22, 26). At 

 the proximal ends they are so compact that it is difficult to 

 make out the double nature, but towards the middle the parts 

 become more separated, and at the distal ends the granules in 

 the chromosomes can hardly be distinguished from the remain- 

 ing chromatin elements, which are still free in the nucleus. 



Separation of the daughter-chromosomes begins at the proxi- 

 mal ends, i.e., at the ends nearest the spindle. Each chromo- 

 some splits down the line of original longitudinal cleavage (Fig. 

 27, A), and the parts move in opposite directions, proximal ends 

 first (Figs. 28, 29). Fig. 38 represents a section through the 

 primary axis, showing the chromosomes in the nuclear plate in 

 the metaphase. Fig. 27 shows the same stage in transverse 

 section. In Fig. 27 the chromosomes have just begun to 

 separate {A), while in Figs. 28, 29 the division is further 

 advanced. During the separation which follows, some of the 

 daughter-chromosomes, moving in opposite directions, pass each 

 other, and a curious crossed appearance results (Figs. 28, 29). 

 Fig. 30 is from a vertical section through the secondary axis, 

 showing an anaphase ; the chromosomes are turned in opposite 

 directions towards the spheres. Fig. 31 represents the same 

 stage in a section cut horizontally through the secondary 

 axis. 



As the daughter-chromosomes separate, the nucleus again 

 elongates, but in a direction at right angles to that of its 

 original elongation, i.e., in the direction of the secondary axis 

 (Figs. 5-20, 30). During this secondary elongation the nuclear 

 lips are pressed more closely together above the central spindle 

 until in some cases a mere slit is all that is left of the former 

 opening (Fig. 17). 



d. Telophase. — The description of nuclear division given 

 above may apply equally to vegetative division or to that occur- 

 ring in spore-formation. The telophase is, however, essentially 

 different in the two cases. In the former, after the chromo- 

 somes are completely separated at the distal ends, the nucleus 



