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THE YELLOW PERCH 
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That branch of the biological sciences 
which is devoted to the study of fishes, 
has long been known as Ichthyology, the 
term being derived from two Greek 
words meaning, when combined, a trea- 
tise on fishes. As in the case of any other 
group of animals, in studying them we 
not only turn our attention to the consid- 
eration of their external forms, their 
color, and the structure of their topo- 
graphical parts, but, in addition thereto, 
the study of the geographical distribution 
of fishes; their anatomy as a whole; 
their habits and ecology, and, finally, as 
much as can be discovered through re- 
search of fossil fishes and their distribu- 
tion in space and time—that 1s, pal- 
aeoichthyology. 
Fishes are now divided into a number 
of classes, which, when taken on the 
whole, include all the back-boned or ver- 
tebrate types of animals almost entirely 
aquatic in habits, which breathe by means 
of gills or branchiae, the air thus obtained 
8 Pd OP OT Os AP 
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History of Ichthyology. Part 1 | 
MAJOR R. W. SHUFELDT, Medical Corps, U. S. A. 
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PHOTOGRAPH BY THE AUTHOR 
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Instead of 
terrestrial animals, 
fishes have the structures known as fins 
being dissolved in the water. 
limbs as seen in 
to which are added, in many species, me- 
dian or unpaired ones of like structure. 
The heart is two-chambered (atrium and 
ventricle) ; while, as a group, fishes are 
as a rule oviparous, the exceptional few 
being viviparous. Their skin may be 
smooth and scaleless, or covered, as in 
most cases, with beautiful scales, varying 
greatly in form, size, and coloration. 
Sometimes these scales are so large as to 
form veritable plates or bucklers, and 
in many instances are variously modified 
for special purposes. A consideration of 
all these departments of ichthyology 
covers an immense field for research, an 
extremely small part of which is at pres- 
ent known. 
In tracing the relationships of fishes, 
we find that they almost imperceptibly 
pass into the Batrachia above them in 
the scale, while below they tend to merge 
