II. The Cytology of the Gametophyte Generation. 203 
Literature. 
Bornet et Thuret, 1878 : Etudes phycologiques. 
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1898 : Phil. Trans, xc. 
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„ „ ,, Bd. xiv, Heft 4. 
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1900 : Annals of Botany, xiv. 
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1898 : Reproduction in Dictyota. Rep. Brit. Assoc., Bristol, 1898. 
• 1903 : Alternation of Generations in the Dictyotaceae. New Phytologist, ii. 
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„ ,, ,, Bd. xiii, Heft 1. 
explanation of figures in plates 
XII, XIII, AND XIV. 
Illustrating Mr. Lloyd Williams’s paper on the Dictyotaceae. 
For convenience of comparison the same scale of magnification has been preserved throughout, 
all the figures having been drawn with the camera lucida under the Zeiss apochromatic oil-immersion 
objective 3.0 mm., aperture 1-40, with ocular 8. 
The development of the Oogonium. 
Fig. 1. The rudiment of the oogonium before stalk-cell division. 
Fig. 2. Prophase. The spirem has segmented, and the nucleolus is becoming vacuolated. 
Fig. 3. A stage further; the chromosomes are longitudinally split, and the nucleolus is breaking 
up into fibrillae and the usual globule. 
Fig. 4. Stalk-cell division spindle. The cordate form is due to contraction, the nucleolar 
globule and fibrillae are present. 
Fig. 5. Polar view of the equatorial plate, showing the curved form of the chromosomes ; the 
number is sixteen. 
Fig. 6. Dispirem of the nucleolus of the oogonium, showing the increase in size of the chromo- 
somes before fusion. 
Fig. 7. Telophase stage of the nucleus of the oogonium, showing a number of deeply stained 
masses embedded in lighter staining substance. 
The development of the Antheridium. 
Fig. 8. Rudiment of the antheridium, the nucleus in the prophase of stalk-cell division. 
Fig. 9. Telophase of the stalk-cell division ; the stalk-cell nucleus has descended into the 
vacuolated basal region. 
