Fig. 1.

Microphotographs of Nissl and Klüver–Barrera tissue staining of primary visual cortices of selected species. The clear pattern of the Gennari line seen in the macaque is also very clear in the giraffe, which heavily relies on vision. It is also noticeable in the deer and sheep, but is not equally present in aquatic mammals. In the bottlenose dolphin, a hint of myelin double band is visible. This is less true in Cuvier’s beaked whale, and unnoticeable in the fin whale. The quality of the tissue might negatively influence myelin staining of the Klüver–Barrera in some cetacean species. All bars are 1 mm