Recordings from the intrinsic tectal cells of the perch have allowed a classification of visual units on the basis of receptive field type. Comparisons with retinal and tectal cells in carp, goldfish, pike, trout and in the Anura were made. Most striking are cells with vertical bar-shaped features forming part of the R.F. The relation between the receptive fields of units lying adjacent within the tectum, suggests that parts of the same pattern are derived from cells within the same vertical column.