Fig. 2

Cleavage of A. lata embryo. a Early stage 1 after zygote deposition. b First polar body formation. c Second polar body formation. d Teloplasm formation during late stage 1. e Stage 2 where the first asymmetric cleavage (AB + CD) occurs. f Early stage 3, in which the second asymmetric cleavage (C + D) takes place. g Late stage 3 showing the third asymmetric cleavage (A + B) with teloplasm being segregated to the D macromere. h Stage 4a, in which the first micromere quartet is formed. i Stage 4b, defined by the obliquely horizontal cleavage of macromere D’ which forms meso and ectodermal precursors DM and DNOPQ. j Animal view of stage 4c showing the right M teloblast, originated from DM proteloblast, and DNOPQ’ cell. k Vegetal view of stage 4c showing the left M teloblast. l Division of cell DNOPQ"' into left and right NOPQ proteloblasts during Stage 5. m NOPQ" cells form N teloblasts and OPQ proteloblasts in Stage 6a. n Stage 6b, marked by the division of OPQ” into OP proteloblasts and Q teloblasts. All images in animal view unless indicated otherwise. Scale bar in all images 100 μm