208 
and Etheostoma nigrum from the lakes show no external marks by which the sexes 
can be separated. By examining the glands, however, the sexes can readily be 
distinguished even in individuals only 25 mm. long (about two months old in case 
of E. caprodes). 
Below are given a series of tables which contain the counts of the fins for 
much of the material to be described in the following pages. In all the tables 
the counts are given for the sexes separately in the first two columns and for the 
sexes combined in the third column. The first item is the number of specimens 
examined of each brood. The details of the spinous dorsal, soft dorsal and anal 
fin follow in the order given. Where it has been possible the broods and ages 
have also been given separately, so that it is possible to compare not only the 
sexes with each other, but also the same sex in the two lakes in the different 
broods and ages and in the two species. 
It needs but a glance through these tables to show that the two sexes do not 
differ materially from each other, and that for all purposes of comparisons that 
are to be made in this paper the sex may be dropped out of consideration. It 
seems advisable, however, to consider in brief the details of some of the tables. 
In Table I are given the counts for 1,275 specimens of Etheostoma caprodes 
from Tippecanoe Lake. These fall into two broods—that of 1896, 500 in number, 
taken the same summer (marked ’96°), and that of 1895, 500, taken the same sum- 
mer (marked ’95°), and the remaining 275 the following summer (’95°). In the 
first three columns is given the brood of ’95°, and in the second three columns the 
brood of ’95 after the individuals had attained an age of one year. In the third 
column is given the brood of ’96°. 
Without considering the differences that may exist between the different 
broods or between the different ages of the same brood, we may notice some things 
about the two sexes within the same brood or age. 
1. In all of the structures the percentages are strikingly similar for any given 
number of rays or spines. 
2. The nature of the variation in both sexes isthesame. When this is sym- 
metrical in one sex, we find the same symmetry in the other sex and vice versa. 
This similarity in symmetrical variation in the two sexes is well illustrated in the 
anal fin of the broods of 96°. Here the pervailing number of rays is 11, 57.20% 
having this number in the males and 60.80% in the females. In the males, 20% 
have 10 and 22% have 12. To correspond to this in the females, 19.20% have 10 
and 19.60% have 12. The dorsal rays in the broods of ’95° show asymmetrical 
variation very well. Here the prevailing number of rays is 16, 50%, having this 
number in the males and 48.40% in the females. In the males, 39.60% have the 
