MEANING OF THE POLAR GLOBULES. 



13 



Ilia. 



e.c. 



III6, 



XII. 



Ilia. Only the female pronucleus is shown in this figure. The skein of this is contracted and 

 thickened. The attraction-sphei'es are near one side of the ovum, and are connected with its periphery 

 by a cone of fibres forming a polar circle p.c. ; e.c. equatorial circle. 



III6. The pronuclei have approached one another, and the spindle-system is now arranged across 

 their common axis. 



IV. Contraction of the skein and formation of two V-shaped chromatin filaments in each pronucleus. 



V. The V-shaped chromatin filaments are now quite distinct ; the male and female pronuclei are in 

 close contact. 



VI., VII. The V-shaped filaments are splitting longitudinally; their structure of fine granules of 

 chromatin is apparent in VII. , which is more highly magnified. The conjugation of the pronuclei is 

 apparently complete in these figures, but according to v. Beneden's description, the outlines of both 

 can, under favourable conditions, be still made out. The attraction spheres and achromatic spindle, 

 although present, are not shown in IV., V., VI. and VII. 



VIII.' Equatorial arrangement of the four chromatin loops in the middle of the now elongated ovum : 

 the achromatic substance forming a spindle-shaped system of granules with fibrils radiating from the 

 poles of the spindle (attraction-spheres) into the protoplasm ; commencing division of the ovum into 

 two cells. 



IX. Shows diagrammatically the commencing separation of the chromatin filaments of the con- 

 jugated nuclei, and the system of fibres radiating from the attraction-spheres, p.c. polar circle ; 

 e.c. equatorial circle ; e.c. central particle. 



X. Further separation of the chromatin filaments. Each of the central particles of the attraction- 

 spheres has divided into two. 



XI. The chromatin filaments are becoming developed into the skeins of the daughter nuclei. These 

 are still united by achromatic fibres. The protoplasm of the ovum is becoming divided. 



XII. The daughter nuclei exhibit a chromatin network. Each of the attraction-spheres has divided 

 into two, which are joined by achromatic fibres, and are connected with the periphery of the cell in 

 the same manner as the parent sphere shown in Ilia. 



