12 
Northcutt 
struct the probable phylogenetic history of 
brains “from fish to man,” but rather to 
sample the variation that exists in the brains 
of living taxa and to recognize common mor- 
phological patterns and their adaptive sig- 
nificance, Only by sampling the variation that 
exists can patterns of common adaptation be 
recognized. Once these patterns are iden- 
tified, hypotheses about their biological sig- 
nificance can be formulated and tested. 
In this paper I review studies on the 
organization of the forebrain and midbrain 
of lizards and report new observations on 
their morphological variability and histo- 
chemical organization. Two distinct patterns 
of neural organization are recognized in 
living lizards, and the adaptive significance 
of these patterns is discussed as well as 
their possible significance for understanding 
the phylogeny of lizards. 
Several of the illustrations in this review 
are taken from a manuscript in preparation 
with Dr. David Senn of the Zoological Insti- 
tute of the University of Basel. Many of the 
interpretations of tectal structure and phy- 
logeny presented in this paper have been 
developed as part of our collaboration. 
METHODS 
Representatives of the saurian families 
listed in Table 1 were studied; the nomen- 
clature follows the usage of Underwood 
(1971). Most of the brains were dissected 
from the heads, embedded in paraffin, and 
sectioned in the transverse plane at 15 /t. If 
an animal was very small, the entire head 
was sectioned. Sections were stained with a 
modification of the Bodian silver impregna- 
tion technique (Senn, 1966) or with cresyl 
violet. 
Possible intraspecific variation in de- 
scribed neuroanatomical characters was 
checked by means of multiple brain series 
(N=20-20) for Lacerta sicula, Gekko gecko, 
and Iguana iguana. At the present level of 
analysis, no intraspecific variation was noted 
in the brain characters or features described. 
Many of the morphological characters de- 
TABLE 1. LIZARD SPECIES EXAMINED 
Dibamidae Anelytropsis papillosum 
Dibamus bourreti 
Gekkonidae Coleonyx variegatus 
Gekko gecko 
Ptyodactylum kasselquisti 
Sphaerodactylus cinereus 
Tarentola mauritanica 
Pygopodidae Lialis burtonis 
Xantusiidae Xantusia vigilis 
Iguanidae Anolis carolinensis 
Basiliscus basiliscus 
Callisaurus draconoides 
Crotaphytum collaris 
C. wislizeni 
Ctenosaura hemilopha 
Dipsosaurus dorsalis 
Enyaliosaurus 
quinquecarinatus 
Iguxma iguana 
Phrynosoma comutum 
P. platyrhinos 
Sceloporus magister 
S. undulatus 
Agamidae Agama pallida 
A. stellio 
Calotes versicolor 
Draco sp. 
Physignathus lesueuri 
Chamaeleonidae 
CJiamaeleo bitaeniatus 
C. chamaeleon 
C. jacksoni 
Scincidae Ablepharus kitaibelii 
Chalcides chalcides 
C. ocellatus 
Eumeces algeriensis 
Mabuya vittata 
Scincella laterals 
Ophiomorus latastii 
Lacertidae Lacerta sicula 
L. trilineata 
L. viridis 
L. vivipara 
Teiidae Ameiva ameiva 
Bachia intermedias 
Cnemidophorus sexlineatus 
C. tigris 
Dracaena guianensis 
