384 Coe and Kunkel— California Limbless Lizard. 
lateral borders of the cloacal opening. Proximally it occupies the 
median and posterior borders of the phallus, but ascends spirally 
toward the summit, making a turn of nearly 180° (pl. xxrv, fig. 32). 
A cross section of the phallus near its proximal end shows that the 
groove is not radial in position but nearly tangential, cutting into the 
body of the organ very obliquely. The bottom of the groove is con- 
siderably broader than the superficial portion. In certain reptiles 
the groove is so broad at its bottom as to become T-shaped or even 
anchor-shaped in cross section. Toward its distal end, however, the 
groove becomes shallower, and situated more nearly radially (pl. 
xiv, fig. 29). The phallus is somewhat swollen distally, and is ter- 
minated by a broad, flattened face, across which the spiral groove 
continues as a shallow depression (pl. xiv, fig, 32). This depression 
divides the terminal face of the organ into two practically equivalent 
portions, in each of which is situated a conspicuous pit-like depres- 
sion of somewhat irregular shape, which may be called the terminal 
pit (pl. xurv, figs. 29, 32, ¢.p). 
These terminal pits are much more conspicuous in the embryos 
than in the retracted phallus of the adult male, so that we do not 
ascribe to them any very important function. In the embryos the 
pits are glandular in structure, but in the adult they are lined with 
stratified epithelium not very different from that which covers the 
body of the phallus. Since the phalli arise as outgrowths from the 
lateral borders of the cloacal aperture, they are covered externally 
with ectodermic epithelium continuous with that of the outside of 
the body, as shown in pl. xu1v, fig. 27. The ectoderm of the phalli, 
however, is naturally much thinner and more delicate than that form- 
ing the scaly covering of the body, although it is made up of strati- 
fied scaly epithelium. The deeper cells of this epithelium form a 
well marked Malpighian layer, while the SU pera, scaly cells are 
reduced to one or two layers. 
The phallus is redrawn into its position posterior to the cloaca by 
means of two retractor muscles, the larger of which—the retractor 
phalli magnus—extends quite to the distal end of the organ, where it 
is inserted immediately beneath the two terminal pits. By the con- 
traction of this muscle the terminal portion of the phallus is redrawn 
into the more proximal by a process of invagination similar to that 
of the invagination of the finger of a glove. The epithelium which 
covers the phallus in its everted condition thus comes to occupy the 
center of the invaginated or retracted organ, and forms the lining 
of a slender tube extending throughout its length. This tube extends 
far behind the cloacal aperture and lies parallel with the longitudinal 
