A variable species, but all forms have intermediaries.
Body (excluding appendages)
Up to 26 mm long. Translucent white, usually with a streak of white opaque pigment running from front edge of head to tip of tail, bifurcating to go round the pericardium. On adults, streak is a dorsal line, but on juveniles a wide diffuse band covering much of dorsum [image1]. Sometimes diffuse white pigment on flanks of juveniles .
Arranged in distinct rows on each side of the body . About 3 per row on 3mm long juvenile, about 6 per row at 15mm, larger specimens up to 8 per row. Translucent, revealing green , blue, grey-brown  or almost black internal digestive gland. Forms with surface pigment most fully developed have two orange bands with intervening blue band which conceal most of digestive gland . On some the blue is missing . At the minimum, only the terminal orange band is present . Apex translucent revealing orange cnidosac .
Smooth translucent with diffuse pigment flecks and suffused pale lemon .
Circular outline in ventral view .Translucent white. Rose pink interior of head visible on juveniles .
Oral tentacles translucent with pigment flecks, suffused pale lemon .
Rounded propodial swellings often prominent on adults, but no propodial tentacles . Sole translucent white.
- Cerata have green digestive gland and swollen white or yellow internal cnidosacs filling tips, (Don’t confuse with surface pigment).
- White or pale yellow pigment marks on front of cerata, and, sometimes, in a thin indistinct subterminal ring.