The Golgi architecture of the nucleus caudatus in rabbit, cat, monkey and human material was analysed. The brains were prepared by Golgi--Kopsch impregnation. The fairly divergent types of neurons practically belong to two main groups: projective or efferent neurons and local- or interneurons. The efferent neurons -- as it has been confirmed by experimental studies -- establish far contacts with various regions of the brain. According to the Golgi picture, their axon emits several collaterals, which produce local connections. The interneurons have only locally arborizing axon. The are mainly responsible for intrinsic connections of the nucleus. In both main groups of caudate neurons, several types and subtypes were observed. The number of the types and subtypes of the neurons show an increasing tendency in the phylogenetic series.