Cerebral eye and pigment granules. A–C LM images with regard to the cerebral eye (dashed arrows), frontal aggregations and streams of pigment granules (normal arrows) A Distinct frontal aggregations of pigment granules present, cerebral eye of normal size (S. triophthalma) B Frontal aggregations and streams of pigment granules are absent, cerebral eye of normal size (S. pectinata) C distinct streams of pigment granules are present, large cerebral eye (S. baltica). Scale bar: 20 µm.