a22 
In Tippecanoe Lake the anal fin in both species is slightly larger. The nature 
of the variation in the anal fin is quite definite for each lake. Thus from Tables 
VI and X we find that the variation in Tippecanoe Lake is very nearly symmet- 
rical around the prevailing number, 9, while in Turkey Lake the variation is 
pronouncedly asymmetrical, a much greater per cent. varying below nine than 
above. 
On the contrary, the dorsal spines of one species show an increase, and of the 
other a decrease in number. Aside from this exception, however, there is, as in 
the anal fin, a marked parallelism in the nature of the variation in the two species 
for each lake. Thus in Tippecanoe Lake the variation is nearly symmetrical, 
while in Turkey Lake it is very asymmetrical. The asymmetry in Etheostoma 
caprodes is due to the difference in the three broods included, yet, as can be seen 
from Fig. 2, each brood shows this asymmetrical variation in its dorsal spines. 
The soft dorsal in both species has one more ray in Tippecanoe Lake than in 
Turkey Lake. In Figs. 1 and 2 are given the curves for the dorsal rays. In the 
curves for both species the continuous line is for the Turkey Lake specimens and 
the broken line for Tippecanoe Lake specimens. From these it will be seen that 
in Tippecanoe Lake the prevailing number is 16 and 13 for Etheostoma caprodes and 
Etheostoma nigrum respectively, and in Turkey Lake it is 15 and 12 respectively. 
In the dorsal rays, too, the Turkey Lake specimens, in contrast to the Tippecanoe 
Lake specimens, vary asymmetrically. 
The comparison of the two lakes, in so far as these two species are concerned, 
may be briefly summarized as follows: Tippecanoe Lake is characterized by a 
greater number of scales on the nape and rays in the anal and soft dorsal. The 
variations are very nearly symmetrical in Tippecanoe Lake, while in Turkey 
Lake they are decidedly asymmetrical. The proportion of males to females is. 
greater in Tippecanoe Lake than in Turkey Lake. 
This parallelism in the variation of these two species becomes the more inter- 
esting when considered in another relation, namely, that one of the species does 
not thrive equally well in both lakes. Etheostoma nigrum is as excessively rare in 
Turkey Lake as it is abundant in Tippecanoe Lake. One to 50 approximates the 
ratio. On the other hand, Etheostoma caprodes is equally abundant in both lakes. 
The modifications found in these strictures, therefore, can not be attributed to 
any selective influence, or at best, this influence is so slight as to be largely over- 
come in its effect by ontogenic influences. Otherwise we could hardly account for 
the parallel modifications in two rfearly related species living side by side, the one 
thriving, and the other on the point of extermination. 
