A, Veliger-larva of an Opisthobranch (Polycera).
C, Diblastula of an Opisthobranch (Polycera) with elongated blastopore oi.
- Phyllirhoe bucephala, twice the natural size, a transparent pisciform pelagic Opisthobranch.
B, Trochosphere of an Opisthobranch (Pleurobranchidium) showing - shgr, the shell-gland or primitive shell-sac; v, the cilia of the velum; ph, the commencing stomodaeum or oral invagination; ot, the left otocyst; pg, red-coloured pigment spot.
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