Nuclear Division in the Hepaticae. 521 
tions with a passage from one of Boveri’s papers : ‘ Ich meine 
deshalb, es sollte . . . nicht mehr jeder Autor, wenn er an 
einem bestimmten Object die eine Entstehungsart als sicher 
erweisen kann, nun denken, er habe damit aile anders lautenden 
Angaben fur andere Objekte umgestossen und diirfe seinen 
Befund als allgemein gliltig proklamieren.’ 
EXPLANATION OF FIGURES IN PLATES 
XVI, XVII, AND XVIII. 
Illustrating Prof. Farmer’s paper on Spore-Formation in Hepaticae. 
All the Figures were drawn, using Zeiss 2 mm. apochrom. Microsc. with various 
oculars, and are reduced. 
Figs. 1-16. Fossombronia Dumortieri. 
Fig. 1. Spore-mother-cell with nucleus in resting condition. 
Fig. 2. Same a little more advanced, nucleus preparing for division, three 
centrospheres at the angles, where the quadripolar spindle-rays afterwards appear. 
Fig. 3. The same still later, the linin is forming aggregations, and the chro- 
matin becomes prominent. 
Fig. 4. The chromatin aggregations appear as flattened rings, well marked. 
The nucleolus still present, but vacuolated. 
Figs. 5,6. Variations which occur at the next stage, quadripolar spindle. 
Figs. 7, 8. Slightly older cell. The nucleolus becomes much vacuolated. The 
chromosomes more marked. 
Fig. 9. The first spindle. 
Fig. 10. The divided chromosomes retreating, a rudimentary cell-plate shown. 
Fig. 11. The second division. One nucleus is seen in pole-field, with its eight 
chromosomes. The dotted line indicates the position of the first division wall. 
Fig. 12. The four daughter-nuclei, resulting from the last division. They are 
diagrammatically represented in one plane ; in reality the pair with the cell-plate 
between them are alone in focus. The appearance of the division walls seems 
to be simultaneous, and not successive, in this particular cell. 
Fig. 13. The spore-mother-cell after division. The protoplasm is very much 
vacuolated. 
Fig. 14. A young cell of the sporogenous (archesporial) tissue preparing for 
division ; the centrospheres well shown. 
Fig. 15. Later stage of the same, with the chromosomes forming. 
Fig. 16. A spindle from the same tissue, with sixteen chromosomes which have 
just divided (only seven are shown in the drawing). The astral radiations are hardly 
visible at this stage. 
