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IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
nerve. Corresponding* apparently to the levator bulbi of urodele 
and anurous amphibians there is a compressor muscle of the or- 
bital glands, like a true levator bulbi innervated by a branch 
of the ramus mandibularis Y. Inserted upon the sheath of the 
orbital glands is another muscle which acts apparently as a dila- 
tator of these glands, also innervated by the same branch as the 
compressor muscle. 
In Dermophts mexicanus only the internal rectus muscle is 
lacking. There is an extremely vestigial retractor bulbi. The 
retractor tentaculi is a well developed muscle. All three eye- 
muscle nerves are present, but only the abducens is of any con- 
siderable size. A compressor and a dilatator muscle of the or- 
bital glands are present and more strongly developed than in 
Herpele. 
In the larva of Ichthyophis all the eye-muscles are present, 
but only the retractor tentaculi is of functional importance. In 
stages before the tentacle is formed the retractor tentaculi is in- 
serted upon the eyeball. Compressor and dilatator muscles of 
the orbital glands are present. 
In Geotrypetes petersii there are two well formed muscles re- 
lated to the tentacle. One is the retractor tentaculi innervated 
by the abducens; the other is innervated by the oculomotor nerve 
.and evidently corresponds to an internal rectus muscle. It is 
inserted upon the tentacular sheath. The other muscles of the 
eyeball are vestigial. A compressor muscle of the orbital glands 
is present, but not a dilatator. 
Thus we see that in the coecilians the typical amphibian eye- 
ball musculature has been modified first by the degeneration of 
muscles and nerve to the point even of complete disappearance 
in some instances; second by the transfer in function and ana- 
tomical relations of certain muscles from the eyeball to ad- 
jacent organs, as the retractor bulbi transformed into a re- 
tractor tentaculi, the rectus internus changed into a retractor 
of the tentacular sheath, and the levator bulbi modified to com- 
pressor and dilatator muscles of the orbital glands. 
Department of Zoology, 
Grinnell College. 
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