At what stage of development does the somitic mesoblast invaginate into the primitive streak of chick embryo?
D000818:Animals; D001756:Blastoderm / Q000637:transplantation; D002642:Chick Embryo / Q000254:growth & development*; D046508:Culture Techniques; D004475:Ectoderm; D006257:Head / Q000196:embryology; D008648:Mesoderm; D009024:Morphogenesis; D009132:Muscles / Q000196:embryology; D013116:Spinal Cord / Q000196:embryology; D014184:Transplantation, Homologous