702 | The Food of the Darters. { October, 
diptera.! As a tree sends out its roots in all directions in search 
of nourishment, -so each of the larger divisions of animals ex- 
tends its various groups into every place where available food 
occurs, each group becoming adapted to the special features of 
its situation. Given this supply of certain kinds of food, nearly 
inaccessible to the ordinary fish, it is to be expected that some 
fishes would become especially fitted to its utilization. Thus the 
Etheostomatinzee as a group are explained, in a word, by the 
hypothesis of the progressive adaptation of the young of certain 
Percide to a peculiar place of refuge and a peculiarly situated 
food supply. 
Perhaps we may, without violence, call these the mountaineers 
among fishes. Forced from the populous and fertile valleys of - 
the river beds and lake bottoms, they have taken refuge from 
their enemies in the’ rocky highlands where the free waters play 
in ceaseless torrents, and there they have wrested from stubborn 
nature a meagre living. Although diminished in size by their 
continual struggle with the elements, they have developed an 
activity and. hardihood, a vigor of life and glow of high color 
almost unknown among the easier livers of the lower lands. 
The appended table will facilitate a comparison of the records 
of the different genera. The percentages were obtained by esti- 
mating carefully the ratios of each element of the food of each 
individual, and averaging these ratios for all the individuals of a 
species : 
DETAILS OF THE FOOD OF THE ETHEOSTOMATIN. 
; , SORRE Spe Eee 
G E £ E 3/8 $ 2 i 
e 8 et Ste ee EET 
fe} ei aie Flelelais 
B11 el ee] Sl Oe S 
"Sinibes of paina a E E aS 9 
I. Motiv: re eye or 
e ari ewe or 
n INSECTA: ....3... 100 | 99 | 96 |100 | 65 roo | 88 |100 | 36 
1. Diptera +++] 93 | 97 | 73 58 | 43 Ico | 61 | 37 
Undetermined to 12 | or | 07 | 09 | 02:|:35 I0 
momus larvæ , ccc. 81 | 06 | 66 | 49 | 41 | 65 | 61 | 27 | 34 
2. 2 Hemiptera, 25s; By å 13 o5 
ER Rouen es karese 13 05 
inet. a. o3 
Larvæ 7 re ee wee FETTO, | OF 92 
C. mmida UNI E | 06 
2 The Catostom[at]idæ (acker are an exception to this rule, feeding wher 
young chiefly on Algæ and Protozoa 
. 
