538 LESLIE B. AREY 
ard, and Angelucci (’78), on the lizard and turtle, both failed to 
find any influence due to the action of light, although Angelucci 
(90) later demonstrated a rather limited pigment migration 
in the retina of Testudo marina, which has no rods. Chiarini 
(06) reported that a distinct but limited pigment expansion 
was observed in the light-adapted eyes of the lizard. Finally, 
Garten (’07) found no significant differences in the light- and dark- 
adapted eyes of Lacerta, Emys, and the chamaeleon, although 
he admits that with strong illumination (as the dazzling Italian 
sunlight used by Chiarini) satisfactory preparations from 
Lacerta might be obtained. 
In the retinas of birds, which usually possess both rods and 
cones, the pigment migration according to Chiarini (’06) is 
more pronounced than in reptiles. Stort (87) showed this to 
be true both in areas of the pigeon’s retina where rods are present, 
and to a more limited degree where they are absent. The 
influence of light was also observed in the hen (Krause 794), and 
in the owl (Angelucci ’78), which are respectively diurnal and 
-nocturnal in their habits. 
The difficulty in obtaining preparations of the mammalian 
retina without separation of the pigmented epithelium and a 
coincident loss of pigment granules, renders exact judgments 
concerning the effect of light, very troublesome. The limited pig- 
mentation of the retinas in this group increases the seriousness 
of faulty technique. Many investigators have regarded the 
adherence of the pigment to the retina as a criterion of the 
influence of light, yet this adherence, as Ewald und Kihne (’78) 
showed, is quite variable. Passing over the work of Angelucci 
(78), who reported definite pigment movements in the rabbit, 
there remains Chiarini’s (’06) description of the slight differences 
observed in the retinas of dogs which were exposed to direct 
sunlight and to darkness. The pigment of the light-adapted 
animals extended in short fringe-like processes between the rods, 
in contrast to the densely contracted pigment of the reciprocal 
set. Finally, Garten (’07) carried out carefully executed ex- 
periments on the ape, ox, rabbit and rat, yet failed to observe 
any striking differences between the effects of light and darkness. 
