80 The Cephalce Veins and Sinuses of Reptiles 
described above, gave a very satisfactory exhibition of the regular moult- 
ing movements, with complete protrusion of the eyes and both stages 
well developed. 
4, CNEMIDOPHORUS SEXLINEATUS behaved in much the same way as 
Lacerta muralis, but after some delay typical results were also obtained 
in this species. 
The difficulties encountered in this case and in Lacerta muralis may, 
perhaps, be explained by the unnatural conditions. It is not improbable 
that in many cases, at least, the actual removal of the exuvie is effected 
in retirement, and that under other conditions the moulting movements 
are performed only occasionally, or as a matter of necessity. The instinct 
to seek seclusion at the approach of the moulting time occurs in snakes, 
and it would apparently tend to develop also among the lizards, since the 
flooding of the sinus orbitalis necessitates at least partial closing of the 
eyes and thus exposes the moulting animal to more or less danger from 
enemies. 
5. UTA STANSBURIANA and SCELOPORUS SPINOSUS appeared somewhat 
shy at first, but after a short interval the moulting movements were exe- 
cuted in a typical way. 
6. PLATYDACTYLUS MAURITANICUS and EUMECES FASCIATUS were ex- 
tremely shy and failed to respond to the court plaster treatment. 
The preceding observations and the earlier studies on Anolis caro- 
liniensis and Sceloporus undulatus show that the habit of flooding the 
cephalic veins and sinuses for moulting purposes is well established 
among the Sauria. The typical process is the normal cycle of intumes- 
cence already described, which includes two distinct stages. . The first of 
these is characterized by gradual flooding and distension of the veins 
and sinuses, with a corresponding intumescence of the soft parts of the 
head. The second stage is marked by a sudden increase of blood-pressure 
in the distended vessels, the protrusion of the eyes is increased and a 
wave of high blood-pressure runs through all venous vessels of the head. 
This complicated process occurs naturally in response to the stimulus 
of the exuviz, or it may be induced in an experimental way by the appli- 
cation of court plaster or other suitable material to the head. The re- 
sponse, however, has the same physiological significance whether it fol- 
lows the natural or the artificial stimulus, and is in all cases distinctly 
a moulting process. 
b. GENERAL CHARACTERISTICS OF THE MOULTING PROCESS. 
A discussion of the work of the moulting mechanism naturally re- 
quires, first of all, a review of certain anatomical peculiarities of the 
