RETINA OF ALLIGATOR MISSISSIPPIENSIS 211 
(Garten) has shown that there are only cones in this region, that 
this matter should be reinvestigated. 
The conditions in the alligator eye Garten uses in substanti- 
ation of his conception of the functional value of the migration 
of pigment in connection with the movement of the visual cells. 
Since he finds the two parts of the retina containing exclusively 
cones or rods, he argues that pigment migration therefore should 
not take place, because the perceiving power of the eye would 
not thereby be in anyway enhanced. Garten calls attention 
to the importance of the fact that the conical visual cells go over 
very gradually into those of rod form, and points out that it is 
exactly at this transition place that Chievitz localized the fovea. 
In two general reviews by Putter ('12) and Franz ('13) the 
conditions found in the crocodilian retina are summarily given, 
but no new matter contributed. It should be recalled that 
Putter is of the opinion that, although some of the elements in 
the reptilian retina may be cyhndrical in form (that is rod-like) , 
they are all nevertheless to be regarded functionally as cones, 
on account of their dendritic mode of connection with the bipolar 
cells. 
METHODS 
The alligators, which were between 45 and 55 cm. long, were 
treated as follows. Two animals were placed in a dark room 
for twenty-four hours, at the expiration of which time one of 
them was rem-oved to bright diffuse dayhght for seven hours. 
'At the end of this time both were killed. The upper jaw, with 
the eyes, was removed with a pair of large bone forceps, bisected, 
and dropped into a large dish containing an abundance of Per- 
enyi's fluid. The time required for this operation did not exceed 
thirty seconds, and in the dark was carried out in the weak 
light from a photographic lamp. The pupil of the all' gator is 
vertical, and when the animals are placed in light the aperture 
remaining after a few seconds' exposure is but a mere sht. The 
pupillomotor reaction is so decisive, characteristic, and easily 
measurable, that experiments have been begun on the relative 
efficiency of spectral lights upon it. These will be reported 
later. 
