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EXPLANATION OF FIGURES ON PLATE X. 
Illustrating Miss Graham’s paper on Centrosomes in Fertilization Stages of Preissia quadrata . 
The figures were drawn with the aid of a Bausch and Lomb camera lucida, the drawing being 
at the level of the base of the microscope j Zeiss i*8 mm. oil-immersion objective, 1*25 N.A., and 
oc. 4. Magnification about 1431 x. 
Fig. 1. Section of the egg-cell. The membranes of the egg and antherozoid nuclei are in con¬ 
tact. Centrospheres lie at the poles of the egg nucleus. 
Fig. 2. The contents of the egg nucleus of Fig. 1. 
Fig. 3. Section of the egg-cell in which the nucleus of the antherozoid lies in the cytoplasm 
near the egg nucleus. Centrospheres lie on either side of the egg nucleus. 
Figs. 4, 6. Polar views of centrospheres lying on either side of the egg, and antherozoid nuclei 
shown in Fig. 5. 
Fig. 5. The egg and antherozoid nuclei situated between the centrospheres represented in 
Figs. 4, 6. 
Fig. 7. Two cells of a four-celled embryo. Part of the nucleus and the other centrosphere of 
each cell are in another section. 
