| OCR Text |
Show 58 PLATE V WHOLE 1. A Fig. 2. A .. dorsal view by transmitted light of the primitive The blastoderm has begun to show differ pit stage. ential thickening forming distinct protocephalic A lobes Fig. 4. transmitted lateral view by reflected light of the first step The primitive in the organization of the embryo. pit (pp) is on the posterio-ventral aspect of the egg 3. OF EARLY DEVELOPMENT light of the incubated egg at The of the completed cellular blastoderm. vitelline membrane and chorion (Ch) surround the distinctly cellular blastoderm (BId) which in turn surrounds the mass of yolk platelets (Yp). view by the stage Fig. Fig. MOUNTS (Pcp). view by transmitted light of the The thickness of the proto stage as above. cephalic lobes is now clearly evident. A dorso-Iateral same Fig. 5. ventral view by reflected light of the embryo It is clearly divided into prior to blastokinesis. the protocephalon (Pcp) and the protocorm (Pcm). External segmentation has begun as indicated by the The mandibulary (MdS) and maxillary segments.. gastral furrow (Gf) divides the protocorm. Fig. 6. A A view by transmitted light of the same The roots of the amnion are indi above. cated (Am-a and Am-p) but the central portion and the serosa are omitted as they were not visible in the living eggs used as the basis of these drawings. Note that the caudal end of the germ band (Gb-cd) is curved deeply intp the yolk. lateral stage Fig. 7. A as ventral view by reflected light of end of anatrepsis. Only a small the an embryo at portion, the protocephalon and the mandibular and maxillary segments, remain on the ventral surface (MxS) .. Fig. 8. lateral view as shown evident on the A by transmitted light of the ffame in Figure 7. The gastral furrow is unsubmerged portion of the protocorm. The posterior half of the embryo is within the yolk except for a subterminal portion of the posterior stage end. |
