Hoplonemertean larvae
NOTE: It is likely that the larvae of many hoplonemerteans (e.g., Emplectonema sp. 1, Paranemertes californica, Poseidonemertes collaris, Gurjanovella littoralis, Tetrastemma bilineatum) start out with just a single pair of eyes, and possibly, develop more pairs before settlement because adult individuals often have many more eyes.
Most hoplonemertean larvae have paired eyes and an inconspicuous apical tuft. These characters will help you differentiate species:
One pair of small black eyes and statocysts present in cerebral organs. Long, slender larva. Fast swimmer.
Two pairs of eyes with posterior pair difficult to differentiate and appears as one. Larva small, orange in color, and with slightly pointed posterior.
Larval body very green in color, with one to two pairs of eyes. Short, inconspicuous apical tuft present.
No statocysts, not orange or green and with one or more pairs of eyes.