PHOTOMECHANICAL CHANGES IN THE RETINA 543 
Among certain other animals, however, the response of the 
rod myoid to light unquestionably consists in an elongation 
(figs. 3 and 4). Stort (’86) first showed the movements of the 
rods of the crow to be more extensive than the limited changes 
in amphibians. In dark-adapted retinas the rods were much 
retracted, while in the light they were extended toward the 
choroid, and the inner members, which previously had been thick, 
were now tenuous. 
H. Miiller (57), long before, had observed this higher position 
which the inner member of rod cells occasionally assumed and 
since the action of light on these elements was at that time un- 
known, he believed it to be due to faulty preservation. 
Garten (’07) confirmed the results of Stort on the crow and the 
pigeon and extended the work to include the rods of the hen. 
In an owl (Syrnium aluco) as a type of nocturnal bird he could 
discover no significant changes. 
Among the fishes Stort (87, p. 344) also recorded that in the 
light, ‘‘la limite des segments externe et interne est située beau- 
coup plus haut que chez la perche a lVobscurité,’’ yet this state- 
ment for a long time remained unnoticed. Pergens (’96) was not 
able to demonstrate satisfactorily the fine rods of Leuciscus, yet 
he assumed, although wrongly, that their movements corre- 
sponded to those of the cones. Chiarini (’04a), with good fix- 
ation, found no significant changes in the position of the rods of 
Leuciscus and further (’06) denied the occurrence of move- 
ment in the rods of all vertebrates. Garten (’07), however, 
states positively that elongation of the rods of Leuciscus does 
occur in the light, as it certainly does in many other fishes that 
have since been investigated (figs. 8 and 4). Garten further 
showed that in the eel, the rods undergo movements, although 
the cones do not, and accordingly these changes in the rods can 
not be passively brought about through the movements of the 
cones. No movements, however, were observed in the rods of 
Seyllium and Torpedo—the retinas of these fishes lacking cones. 
In general, it may be safely asserted that there are positional 
changes as a response to light in the rods of all fishes which 
possess cones. 
