66 The Food of Fishes. 



specimens of this ^enus were taken from small mud-holes, 

 favorable to the occurrence of Entomostraca of that order. 

 The uniformity of food at this time implies that the selective 

 apparatus of these fishes, whatever its construction, has not 

 yet grown beyond the size of these minute animal forms. 



From the second table of one hundred and six specimens 

 we learn that with a general change of food from Entomos- 

 traca and Ohironomus to larger Crustacea and insects, there 

 appear certain differences, — notably the continuance of 

 Entomostraca as the most important element in Pomoxys, 

 and the occurrence of mollusks in Eupomotis and of fishes 

 in Micropterus. It is important to recall, at this point, that 

 Pomoxys has the largest, finest and most numerous gill- 

 rakers of the group, — the best s^r^^nmj^ apparatus, in short, 

 — that Eupomotis has stout, blunt pharyngeal teeth, and 

 that the black bass have relatively the widest mouths 

 of all. It is also to be noted that the large-mouthed bass 

 commenced to take fish when an inch and a quarter long, 

 and the small-mouthed species not until it reached a length 

 of two and a half inches. 



It will also be observed that Entomostraca are least 

 abundant in the food of the small-mouthed black bass and 

 the rock bass, — species found usually in swift and shallow 

 water, when of this size. The importance of water-bugs 

 (Corixa) to the first three species of this table is evident. 



From the table of adult food we find that these com- 

 mencing peculiarities of the preceding table become here 

 more prominent. All the Entomostraca of this table, ex- 

 cept insignificant traces, now appear in the food of Po- 

 moxys ; the molluscan food of Eupomotis is nearly five 

 times that of any other genus ; and the ratios of fish food, 

 running from eighty-six per cent, down to nothing, when 

 arranged in a series, are seen to correspond, with curious 

 exactness, to a series of the species themselves arranged 

 according to the relative sizes of their mouths. 



I was disappointed in being unable to find any food 

 characteristics corresponding to such minor differences in 

 the length of the gill-rakers of the anterior arch as appear 

 in Lepiopomus, Apomotis, etc., on the one hand, and Xen- 

 otis and Eupomotis on the other. If such peculiarities 



