Embryonic phenotypes from RNAi by feeding versus injection. (a) Wild-type N2 embryos divide with the AB (anterior cell) spindle oriented along the dorso-ventral axis and the P1 (posterior cell) spindle along the AP axis to create a four-cell embryo (d). In wild-type embryos, AB is larger and divides slightly before P1. For par-2, RNAi by both (b) feeding and (c) injection results in embryos in which AB and P1 are of equal size and divide synchronously, with both spindles oriented along the dorso-ventral axis. Embryos in (a-c) are undergoing the second mitotic divisions. For bir-1, RNAi by both (e) feeding and (f) injection results in embryos that do not complete cytokinesis and thus form a single multinucleate cell. Embryos in (d-f) have undergone two rounds of mitosis. Anterior is to the left in all panels.