As stated in the first paper of this series (Crouch, '34)' the purpose of this work is to give a description of the nuclear structure of the diencephalon of Macacus rhesus derived from methods of study which have been used extensively of late on other mammals. It seems that such a study of this portion of the brain is necessary as a basis for an accurate study of fiber connections and for experimental work. Friedemann ('12) has described the subthalamus and hypothalamus in his description of the diencephalon of Cercopithecus ; and Griinthal ( '30) described the hypothalamic nuclei of Macacus rhesus and compared them to those of the rabbit. Both of these papers represent extensive work, but a more detailed study of the subthalamus and hypothalamus in Primates and a comparison of findings with recent descriptions in other animals are important.
The nuclei of the hypothalamus and the subthalamus of lower mammals have been described along with descriptions of the whole diencephalon by Gurdjian ( '27) on the rat ; Pines ('27) for Lemur catta; Rioch ( ' 2 9 a a n d b ) for Carnivora; Ingram, Hannet and Ranson ('32) for the cat; and Papez ('32) for armadillo. I n addition to these should be mentioned Spiegel and Zweig ( '17), Greving ( '25)' Gagel ( '28), Groschel ( '30)' Morgan ( '30), and Krieg ( '32)' who described the hypo-