My larva had at least 4 lobes, more likely 6 (two ventro-lateral, two dorsal-lateral, and two unpaired). One can see clearly two of the lobes in focus in these pictures. The lobes are often retracted or flattened when the larva is under the coverglass. Note the dark green branched gut inside the larva. Polyclads, in general, are characterized by a multilobed gut. Many Müller’s larvae apparently require food in order to reach metamorphosis but only a few species have been observed to feed in the laboratory on microscopic algae (Rawlinson 2010 and references therein).
Martín- Durán, J. M. and Egger, B. 2012. Developmental diversity in free-living flatworms. EvoDevo, 3:7.
Rawlinson, K. 2010. Embryonic and post-embryonic development of the polyclad flatworm Maritigrella crozieri; implications for the evolution of spiralian life history traits. Frontiers in Zoology 7: 12.
Smith NF, Johnson KB and Young, CY. 2002. Platyhelminthes. In: Atlas of Marine Invertebrate Larvae. Edited by C. M. Young. Academic Press. New York.