GRAHAM: CENTROSOMES IN PREISSIA 325 
Centrosomes have been observed in the divisions just preceding 
spermatogenesis and as blepharoplasts, during the metamorphosis 
of the antherozoid mother cell. From my studies it is evident 
that they are also present in the fertilized egg at the time when 
the pronuclei are paired. 
LITERATURE CITED 
Farmer, J. Bretland, & Reeves, Jesse. Оп the occurrence of centro- 
spheres in Pellia epiphylla, Nees. Ann. Bot. 8: 219-224. 1894. 
Kruch, Osvaldo. Appunti sullo sviluppo degli organi sessuali e sulla 
fecondazione della “Riella Clausonis Let." Malpighia 4: 403-430. 
1890. 
Van Hook, J. M. Notes on the division of the cell and nucleus.in 
liverworts. Bot. Gaz. 30: 394-398. 1900. 
EXPLANATION OF PLATE 8 
The figures were drawn with the aid of a Bausch & Lomb eee the 
drawing being at the level of the base of the miscrocope; Zeiss 1.8 mm. oil-immersion 
objective, 1.25 N. A., and oc. Magnification about 1431 diameters 
Figures I and 2 are skisthes of drawings made for another art 
IG. I. A section of the egg cell. The membranes of the egg 224 antherozoid 
nuclei are in contact. Centrospheres lie at the poles of the egg nucleus. 
Fr A section of the egg cell in which the nucleus of the antherozoid lies in 
the билерин near the egg nucleus. А centrosphere appears at the poles of the 
egg nucleus. 
Fic. 3. A slightly younger stage of fertilization. Опе centrosphere is shown 
above the egg nucleus. 
Fic. 4. Polar view of a centrosphere lying in the cytoplasm of another section 
of the egg shown in figure 3. 
