174 EUOUARl) VAN BENEDEN. 



3. The nucleolus (germinal spot) bi'eaks up abruptly into a 

 large number of fragments which continue to diverge from 

 one another and to spread themselves out into the whole 

 mass of the germinal vesicle. These fragments are of 

 unequal size. There is one of them which is notably of 

 larger size than all the others, and which contains the central 

 vacuole of the old germinal spot. This vacuole is now only 

 surrounded by a thin layer of nucleolar substance, which as 

 looked at appears only as a narrow and irregular ring. The 

 formerly homogeneous contents of the germinal vesicle are 

 now granular, and hold in suspension small bodies of 

 variable form and dimensions which are only the fragments 

 of nucleoli. 



4. All the nucleolar fragments increase a little in volume 

 and become less and less refractive. iSoon they appear as 

 only little clouds with ill-defined contours, forming spots on 

 the uniformly homogeneous ground of the germinal vesicle. 

 They at last completely disappear from view. The frag- 

 ment of the nucleolus which encloses the central vacuole 

 is still visible when all the others have already disa])peared. 

 Soon afterwards the last traces of this body likewise dis- 

 appear. The germinal vesicle, which is still perfectly 

 spherical, is now quite clear and transparent. We can no 

 longer see in it any trace of nucleolus, nor any granule of 

 whatever kind. The contour of the vesicle has become 

 less and less marked, as if the substance of the n^embrane 

 were dissolved at the same time with the nucleus in the 

 nuclear substance. The progressive diminution of refrac- 

 tiveness of the nucleolar substance proceeds side by side with 

 the vanishing of the contour of the germinal vesicle. 



5. Some seconds after the last traces of Wagner's spot 

 have disappeared, the membrane of the germinal vesicle be- 

 comes torn, or rather a hole is formed in it. This solution of 

 continuity always appears in that part of the vesicle which is 

 turned towards the centre of the ovum. The contents of the 

 vesicle immediately flow out through the hole, forming a clear 

 drop outside the vesicle. This little drop has the appearance 

 of a bud or of a hernia. It enlarges very rapidly. At the 

 same time the membrane of the vesicle withers and becomes 

 wrinkled. The germinal vesicle has now withdrawn itself 

 slightly from the surface and has got nearer the centre of the 

 vitellus. It is enveloped on every side by the vitelline pro- 

 toplasm. At one moment it appears as if formed of two 

 clear masses adjacent to each other, which on account of 

 their homogeneous appearance encroach upon the granular 

 ground of the vitellus. One of these is formed by that part of 



