82 Transactions of the Academy of Science of St. Louis 
distributed throughout the nucleus. Definite fiber connections 
are unknown. 
HyPorHALaMIc NUCLEI COMPOSED OF ASSOCIATIONAL NEURONS 
Nucleus Supraopticus Diffusus: The neurons of this nucleus 
lie among the fibers of the supraoptic commissure just dorsal to 
the optic chiasm (ite GUA). They are small, associational 
neurons well supplied with chromidia and, consequently, appear 
very dark in toluidin blue and erythrosin preparations. In some 
neurons the chromidia are more densely aggregated at one side 
of the nucleus than in other parts of the cytoplasm, giving that 
portion of the cell an exceedingly dark appearance. Functional 
connections are unreported but they must be essentially local. 
Nucleus Suprachiasmaticus: This nucleus is located im- 
mediately lateral to the ventral tip to the anterior portion of the 
the third ventricle. Its neurons are spherical to slightly pear- 
shaped and are among the smallest and least abundantly supplied 
which surrounds the centrally placed nucleus. Functional con- 
nections of these neurons have not been reported. 
Nucleus Perifornicalis: The neurons of this nucleus lie 
between the fibers of the descending column of the fornix and 
adjacent to them. They are not definitely separated from the 
neurons in the adjacent gray matter. They are all associational. 
The chromidia form a very thin, incomplete perinuclear or peri- 
pheral ring. Knowledge regarding their functional connections 
is lacking, 
Nucleus Parvocellularis: This nucleus lies in the extreme 
dorsal portion of the hypothalamus, just dorsal to the nucleus 
filiformis lateralis, All of the neurons are associational. The 
