14 University of California Publications in Zoology [Veu-.9 
system in the chameleon. Light and heat rather than moisture 
probably have the most effect on the nervous system (Parker, 
1904). In Phrynosoma light causes an inward migration of the 
pigment and dark, an outward migration. This is true in 
Varanus, Agama and several other lizards, but the opposite is 
true in Anolis (Carleton, 1903). 
For the reason that the coloration varies so widely with the 
substratum, the color characters are omitted from the diagnoses. 
In the case of P. douglassi douglassi the distinetive features of 
the coloration are inserted in the key because the color characters 
are important in distinguishing subspecies. 
On the ventral sides of the thighs, there is developed a row 
of glands, the so-called femoral glands. The ducts, which open 
on a row of enlarged seales, are formed from the stratum corneum 
and are filled with’a mass of yellowish secretion (Shaefer, 1902). 
The glands are supposed to function in coition (Hdwards, 1896). 
REPRODUCTION 
Reproduction in this genus is both oviparous and viviparous. 
Among the oviparous species are Phrynosoma cornutum and 
P. blainvillei. The former is known to dig a hole in the earth, 
deposit its eggs and cover them with sand (Edwards, 1896). 
Several days are needed for incubation. With P. blainvillei, 
however, the young hatch a few hours after the eggs are laid. 
The eggs are from fifteen to twenty millimeters in length and 
are covered by a tough, semi-transparent membrane. They vary 
in number from six to fourteen. P. dowglassi, on the other hand, 
gives birth to numerous young which are able to take care of 
themselves a few hours after they are born (Ditmars, 1907). 
Young are usually produced late in the summer, although a 
specimen of P. blainvillei blainvillei kept in captivity laid its 
eges the last of June. Specimens of the same species were seen 
in the act of coition in the latter part of April and in May. 
The period of gestation is not known. 
Hasirs 
Phrynosoma is the most distinetly terrestrial genus of all the 
iguanids, in form and structure being ill adapted to climbing. 
