outlines of zoology zoology fig 89development of polygordiasafter fraipont a mother sperm cell b c sperm morulas dt spermatozoa 1 ovum with large nucleus 2 two cell stage 3 four cell stage 4 blastosphere 5 gastrula ac archenteron 6 closure of gastrula mouth or blastopore 7 formation of stomodasum st and proctodaeum prf which invaginate to meet archenteron ac 8 complete gut formed 9 elongation of larva ap sp apical spot cil ciliated ring nepk primitive nephridia 10 formation of posterior segments n form of adult polygordius rdp046.jpg from içina sperm View Photo