Expression of ClcentHox in embryos of C. longifissura. (a) Lateral view on the earliest stage of detected ClcentHox expression. Expression is found at the vegetal pole at the site of the closed blastopore (b) Vegetal view at the stage of (a) showing that cells that express ClantHox surround the former blastopore. (c) Lateral view on postgastrula stage. The expression domain is below the ectoderm in two bilateral stripes with a stronger expression in the anterior cells (black arrows). (d) Later stage than (c) shows restriction of the expression domain of ClcentHox to a bilateral cluster of about a dozen cells. (e) Haematoxylin stained histological section of an embryo showing the ClcentHox expression below the outer ectodermal layer. (f) Pre-hatchling with bilateral ClcentHox expression domains that are localized in two separate domains along the anterior-posterior axis. (g) Summary of ClcentHox expression (green) in the juvenile from the dorsal side and left side (h) showing the two separate expression domains of ClcentHox on the left and right side. Asterisk indicates the animal/anterior pole of the embryo. (g, h) Animal to the left.