The structure of the freshwater planarian eyespots is simple,especially the eye of Polycelis sp.,which is composed of a pigment cell and a photoreceptor cell.Planarians are becoming the suitable model system for studying the origin of eyespots and evolution.In this paper,the relationship among the eyespots number,the length of the Polycelis sp.and altitude was analyzed from Qinling Mountains and the Taihang Mountains by statistical methods.The results showed that there was a postive correlation between the ...