452 



SCIENCE. 



[N. S. Vol. XI. No. 273. 



length the stream is overhung by bushes 

 and briars, and is full of sticks and brush. 

 The bed and banks are of black mud with 

 a mixture of sand. In some places the 

 ground is quite boggy. The midday sum- 

 mer temperature of the water in this stream 

 is about 72°. The species of fishes found 

 in this stream are almost wholly different 

 from those found in the lake proper, a fact 

 illustrating clearly the importance of even 

 slight differences in geographic location if 

 accompanied by stable environmental dif- 

 ferences. The principal fishes occurring 

 iQ this creek are Semotilus atromaoalatus, Cam- 

 postoma anomalum, Umbra limi, Lucius vermicu- 

 latus, Notropis cornutus, and young Microp- 

 terus salmoides. Crawfishes were abundant. 



The two new fishes discovered are both 

 darters, one belonging to the genus Sad- 

 ropterus and the other to the genus Etheos- 

 toma. 



I may say, in passing, that the darters 

 are members of the Percidffi or Perch family, 

 to which belong the walleyed pike, the 

 Sauger and the Yellow perch. Sixteen 

 genera and 85 species of darters az-e recog- 

 nized. They are all small, active fishes, 

 usually brilliant in coloration and have 

 much the same position among fishes that 

 the warblers have among birds. 



Both of the new darters obtained at Lake 

 Maxinkuckee were found in Aubeenaubee 

 Creek and nowhere else. 



The nearest relative of the species of 

 Hardopterus is H. scierus, which, though not 

 known to occur in Lake Maxinkuckee, is 

 found in Yellow Eiver of the Kankakee 

 drainage, only a few miles north, and also 

 in Tippecanoe Eiver five miles south of the 

 lake. The form found in the creek is well 

 set off from its nearest relative and is de- 

 scribed as a species. 



The other darter, described as new, is 

 evidently derived from E. iowas, which is 

 found, not only in many of the streams of 

 western Indiana, but also in Lake Maxin- 



kuckee in some abundance. It is, how- 

 ever, not known to occur in Aubeenaubee 

 Creek. 



Etheostoma ioivce, in extending its range 

 from its original center of distribution, in 

 all probability, found its way into Lake 

 Maxinkuckee from the Tippecanoe River. 

 Having once become established in the lake, 

 individuals sooner or later began entering 

 its tributary streams. Among the indi- 

 viduals entering Aubeenaubee Creek there 

 were some that, finding the conditions easy, 

 remained and bred there, and thus a creek 

 colony was established. It is altogether 

 probable that for some, possibly many 

 j'ears, individuals from the colony would 

 occasionally return to the lake and inter- 

 breed with individuals that had never left 

 the lake. And the reverse would also take 

 place : individuals from the lake would 

 probably continue for many years to invade 

 the domain of the creek colony and inter- 

 breed with its members. Under conditions 

 such as these, the members of the colony 

 going farthest toward the head of the creek 

 were probably -the ones which soonest be- 

 came free from the infiuence of the lake 

 and, breeding only among themselves, were 

 modified most rapidly by the new environ- 

 ment. In time they became so well differ- 

 entiated as to render them readily distin- 

 guishable from the parent form in the lake. 

 During the continuance of the conditions 

 mentioned, however, the migration and 

 countermigration between the lake and the 

 stream, there would be found in the lower 

 part of the stream and in the lake about its 

 mouth, the progeny of the individuals from 

 the lake and creek which had interbred. 

 These would possess characters more or 

 less intermediate between the parent spe- 

 cies (E. ioxu(B) and the derived form in- 

 habiting the creek. So long as these inter- 

 mediate forms continued to exist, the form 

 found in the creek would be only an incipi- 

 ent species. As an incipient species it would 



