86 
Cruce & Cruce 
Figure 4. Dark-field photomicrograph of superficial 
layers of the tectum of a Tegu lizard which had 
been given an intraocular injection of tritiated 
proline in the eye contralateral to the illustrated 
optic tectum. The numbers are the same as Figure 
3. Reprinted with permission of Elsevier Pub- 
lishing Co. (Brain Research, 85, 1975. p. 225.) 
tion. In Iguana and AnoUs Butler and 
Northcutt (1971) found that different parts 
of the nucleus receive differential projec- 
tions, i.e., the contralateral projection was 
denser in the medial half of the nucleus 
whereas the ipsilateral projection was denser 
in its lateral side. In the present report such 
differential terminal labeling was not ob- 
tained. We found that the part of the ipsi- 
lateral nucleus receiving retinal terminals 
overlaps with that part of the contralateral 
nucleus which receives retinal fibers. 
Figure 5. Superimposed dark-field and light-field 
illumination photomicrographs of ipsilateral 
retinotectal projection of Tegu lizard. The silver 
grains indicating terminal labeling appear as a 
band of white dots in layer 9 (dark-field illumina- 
tion) ; the darker and somewhat larger structures 
seen in other parts of the photomicrograph are 
neurons (bright-field illumination). Scale bar: 
200m. 
As in the case of the ventral lateral genicu- 
late nucleus the configuration of terminals 
in the GLD does not exactly conform to that 
area labeled GLD as a result of cytoarchi- 
tectonic study. In Nissl-stained material the 
cells and neuropil of the GLD are not well 
differentiated. The terminals, however, form 
two non-overlapping oval areas. In view of 
the present experimental results a reevalua- 
tion of the boundaries of both GLD and GLV 
seems warranted. 
In the present study, a patch of label was 
seen in the dorsal thalamus located between 
the dorsolateral and dorsomedial nuclei. This 
area has not been indicated as a site of 
terminals of retinal ganglion cells in studies 
on the visual system of other lizards. In their 
autoradiographic study in the tuatara, North- 
cutt, Braford, and Landreth (1975) found 
labeling in an area caudodorsal to nucleus 
dorsolateralis anterior; whether or not this 
projection corresponds to what we see in the 
Tegu lizard remains to be determined. 
