Fig. 3. Formation of germ granule in fertilized bisected egg fragments of Sagitta bipunctata. (A) Equal section along the animal-vegetal (AV) axis: the fragment containing the two pronuclei (left) has segmented into four closely apposed cells whose boundaries are not seen in the plane of focus shown (two of the four nuclei are indicated by arrows). The germ granule (GG) has formed in the vegetal cortex of both nucleated (left) and enucleated (right) fragments. (B) Unequal section along the AV axis: germ granules (GG) have sizes proportional to the size of vegetal hemisphere fragments (see inset). (C,D) Same two fragments in two different planes of focus after performing a slightly oblique section with respect to the AV axis (see inset). In C it can be seen that each fragment contains a pronucleus (MP, FP). In the tangential focal plane shown in D, two germ granules (GG) are seen forming in the cortex.
