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Lloyd Williams. — - Studies in the Dictyotaceae . 
Fig. io. Vertical section parallel to the long axis of the thallus. The antheridium has already 
divided transversely. 
Fig. ii. Vertical section transverse to the axis of the thallus. First division of the antheridium, 
polar view of the nuclear plate, showing the number of chromosomes. 
Fig. 12. Vertical section showing border -cells. 
Fig. 13. Vertical section transverse to the thallus. Division more advanced. The inner 
border-cell is seen to the left. 
Fig. 14. Vertical section through a mature antheridium ; the inner border-cell is still undivided. 
Fig. 15. Antherozoids fixed with potassium-iodide iodine in sea- water and stained with methylene 
blue. Nuclei and physodes shown. 
Fig. 16. Antherozoids fixed with dilute Flemming’s mixture and stained by the iron-alum- 
haematoxylin method. 
Fig. 17. Antherozoids fixed with dilute Hermann’s solution and stained with gentian violet. 
At the top left-hand corner is an apparently biciliate, and at the right-hand side of the figure 
a binucleate antherozoid. In Figs. 15-17 the small black dots are physodes. 
Fig. 18. Antherozoids drawn while motile. The small black dot is the red eye-spot, the 
colourless part is the nucleus ; some show the presence of physodes. 
Fertilization and segmentation of the Egg. 
Fig. 19. Section of newly liberated egg fixed with dilute Flemming. There is a zone of ‘ kino- 
plasm ’ round the nucleus, and a radiate arrangement of the chloroplasts. The physodes are at the 
surface of the egg. Of the numerous antherozoids in the neighbourhood three have been drawn. 
Fig. 20. Delayed fertilization. The antherozoid, greatly increased in size, is seen to the right 
of the nucleus, a few are shown outside the membrane. The egg-nucleus is in the prophase of 
parthenogenesis. 
Fig. 21. Fertilized egg-nucleus with male and female nucleoli and a single centrosphere. 
Fig. 22. Prophase of the first segmentation mitosis ; the chromosomes are thirty-two in number, 
the remainder being in two other sections. 
Fig. 23. A later stage ; the chromosomes are split and the nucleoli very irregular in form. 
Fig. 24. Early spindle showing two cones at an angle with each other. The faint radiations 
are better seen in the succeeding section. 
Fig. 25. The completed spindle. 
Fig. 26. Polar view of the nuclear plate, showing the thirty-two chromosomes. 
Fig. 27. The two daughter-nuclei in the dispirem stage ; the nucleoli beginning to differentiate. 
Fig. 28. The daughter-nuclei completed; each has two nucleoli as in the prophase of the 
preceding mitosis. 
Fig. 29. Abnormal fertilization ; a stage later than Fig. 20. 
Parthenogenesis of unfertilized Eggs. 
Figs. 30, 31. Two modes of initiating the parthenogenetic figure. In both the nucleolus seems 
to be directly converted into chromosomes. 
Fig. 32. An exceptionally regular early spindle. Here again the chromosomes seem to be 
directly converted into chromosomes, of which there are eleven in this section and five in the next. 
Figs. 33-36. Four examples of the parthenogenetic ‘spindle.’ It is very multipolar and 
exceedingly irregular, there is no trace of nuclear membrane or of nucleolar substance, and the 
chromosomes are invariably sixteen in number. 
Fig. 37. Vesicles (nuclei) containing one or several chromosomes beginning to differentiate in 
the kinoplasmic mass. 
Fig. 38. An exceptional figure showing the separation of two groups of nuclei with a few 
connecting fibres. 
Fig. 39. Newly formed nuclei with chromosomes. 
Fig. 40. A few nuclei out of a group of twenty ; nucleoli beginning to appear. 
Fig. 41. The only instance observed of a group of nuclei with centrosome and radiations. 
Fig. 42. Parthenogenetic germling in which the nuclei have separated into two groups; a 
septum is beginning to form between the two halves of the cell. 
