THE INDIVIDUALITY AND VARIATION OF THE 
PYLORIC CAECA OF THE CENTRARCHIDAE. 
ROSWELL HILL JOHNSON. 
(With Plates XLI-XLV and two Text-figures.) 
The object of this contribution is to establish that the py¬ 
loric caeca of the Centrarchidae are not similar, as generally 
assumed, but have individuality, and to describe their varia¬ 
tion. 
With the exception of eleven Micropterus dolomieu and 
eight Micropterus salmoides , all the fish were taken from Lakes 
Mendota, Monona, Wingra and Waubesa. These lakes are 
near Madison, Wisconsin, and are in connection with each 
other. The nineteen bass were from Round lake, Langlade 
county, Wisconsin. Record was kept of the localities, but as 
110 significant differences have appeared, the fish of the differ¬ 
ent. localities will be considered together. 
The family Centrarchidae has three American sub-families, 
each of which is represented by species used in this investiga¬ 
tion—the Lepominae, C entrarchinae and Micropterinae. Jor¬ 
dan and Evermann state that the family has five to ten caeca. 
Of the Lepominae, the largest of the three sub-families, 
three species were investigated, Lepomis pallidus (blue gill), 
Ambloplites rupestris { (rock bass) and Eupomotis gibbosus 
(sun fish). 
Lepomis pallidus Mitchill. 
This species has 6-9 caeca, with a mode of 7 and a mean of 
7.4323 ± .0294. The frequencies are given in Text-figure 1. 
The variation measured by the standard deviation was .6882 ± 
.0270. This is very high, as shown by the coefficient 
of variation obtained by dividing the standard deviation by the 
