54 
Wager . — The Nucleolus and Nuclear Division 
EXPLANATION OF FIGURES IN PLATE V. 
Illustrating Mr. Harold Wager’s paper on Phaseolus. 
Fig. i. Resting nucleus, showing the large vacuolar nucleolus and delicate threads suspending 
it to the peripheral network. 
Fig. 2. Peripheral network seen from the surface of a resting nucleus. The linin-network with 
minute chromatin-granules is seen. 
Figs. 3 and 4. Resting nuclei, with nucleoli containing a single vacuole of irregular outline, less 
deeply stained than the peripheral portion. 
Fig. 5. A nucleus, showing the nucleolus with an interruption in the peripheral deeply stained 
portion at one point, giving it the appearance of a flask-like structure enclosing a less deeply 
stained substance. The suspending threads are more prominent and more numerous around this 
opening. 
Fig. 6. Nucleolus of irregular shape with prominent suspending threads. The substance of the 
nucleolus appears as if drawn out into these threads. 
Fig. 6 a. Nucleolus, which had fallen out of a nucleus, showing threads drawn out of the 
substance of the nucleolus. 
Fig. 7. Irregularly shaped nucleolus, showing its substance drawn out into the suspending 
threads. 
Fig. 8. Later stage than Fig. 7. The nuclear membrane not clearly visible. The nucleolar 
threads are prominent. 
Fig. 9. Surface-view of a nucleus at about the stage between Figs. 6 and 8. A portion of the 
peripheral network has become thicker and more prominent, with a delicate linin-network in 
the meshes of it. Compare with Fig. 2. 
Fig. 10. A nucleus, showing the kinoplasmic filaments at the poles. The nuclear membrane 
is still visible. 
Fig. 11. Nucleus, showing the nuclear membrane disappearing on one side, and the penetration 
of the kinoplasmic filaments into the nucleus. 
Fig. 12. Slightly later stage than Fig. 11. 
Fig. 13. The nuclear membrane has disappeared, and the bipolar spindle is now visible around 
the irregular mass of chromosomes and nucleolus. 
Figs. 14-20. Show the formation of the chromosomes. 
Fig. 14. A slightly later stage than Fig. 8. The connexion of the nucleolus with the nuclear 
network is well seen. 
Fig. 15. Later stage. The filaments of the spindle are now in close contact with the nuclear 
network, which has not yet begun to break up into chromosomes. 
Fig. 16. About the same stage as Fig. 15, but from a different point of view. 
Fig. 17. A section taken through a nucleus at a later stage than Fig. 16, showing the segmenta- 
tion of the nuclear thread into rod-like chromosomes. 
Fig. 18. Shows the irregularly lobed nucleolus surrounded by chromosomes. About the same 
or slightly later stage than Fig. 19, but a larger nucleus. The connexion of the nucleolus with the 
chromosomes not visible. 
Fig. 19. Section through a nucleus at about the same stage as Fig. 18, showing nucleolus and 
a few of the chromosomes. 
Fig. 20. The grouping of the chromosomes in the equatorial plane. Equatorial plate. The 
spongy remnant of the nucleolus in the midst of them, less deeply stained, can be seen, with 
apparently some connexion still to the chromosomes. 
Fig. 21. The less deeply stained remnant of the nucleolus shown dividing into two unequal 
parts, one of which will pass to each pole of the spindle. Compare Fig. 23. 
Fig. 22. A nucleolar remnant at one pole only of the spindle. This is surrounded as in a 
resting nucleus by a clearer space across which suspending fibres are seen. 
Fig. 23. Two unequal spherical nucleolar remnants approaching opposite poles of the spindle. 
Each is surrounded by a clear space, and stains much less deeply than the chromosomes. 
