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 several pairs of eyes. These characters will help you differentiate the remaining species.
Larva can be quite large and with well-developed proboscis and three conspicuous pairs of eyes.
Two pairs of eyes, red and/or black in color.
Two pairs of eyes, larva long and with hair-like projections anteriorly.
Larva has one pair of eyes and readily rolls into a sphere when trapped between a slide and coverslip.