56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I25 



gradually contaminated with the fluxed elements from the overflows 

 or discharges of the Chesapeake and Ohio Canal. 



These findings offered interesting problems. The first section of 

 the Chesapeake and Ohio Canal, from Little Falls to Seneca, Md., 

 was opened in 1830, while the rest, Seneca to Cumberland, Md., was 

 opened to water travel in i860. This canal covered a stretch of 186 

 miles. In 1896, when I went to Washington, the Canal was used 

 extensively to carry huge barges of coal from Cumberland to 

 Washington and other freight northwestward. These barges served 

 as carriers for the Washington complex of Goniobasis that had 

 attached themselves to the bottom and sides of the barges while an- 

 chored at Washington. This, therefore, was the explanation for the 

 fluxed condition of the Chesapeake anl Ohio Canal Goniobasis fauna. 



The smooth Shenandoah and the multilirate lower Potomac Gonio- 

 basis faunas suggested two species, mutually fertile, that at their 

 meeting place crossed and produced the endless number of mutants 

 now found there. 



Cage breeding in the Shenandoah, Roaches Run, and Fort Belvoir 

 furnished confirming evidence that the fluxed condition in the Potomac 

 was due to the crossing of the smooth and multilirate species at their 

 meeting contacts. 



This process of hybridizing and mutating is going on all about us. 

 The various breeds of dogs, cattle, pigeons, fowls, Drosophila, and 

 most of our cultivated plants tell a marvelous confirming story ! Here 

 man's selection of what he wishes to preserve expedites fixation, 

 which in the unaided field of nature works slowly and haphazardly 

 with the survival of the fittest. The human hodgepodge is no 

 exception. 



The microcosms of chemical compounds contained in the chromo- 

 somes and fluids of germ cells convey not only the spark we call life, 

 but their specific composition determines and assures that the end 

 of the developing offspring shall be of the parents' kind, i.e., when 

 the mating of the two parent germ cells are of the same kind. When 

 germ cells of nonrelated species meet, we believe that they are not 

 attracted to each other or are incompatible, or in instances where fertili- 

 zation takes place the resultant embryo fails to run a complete course 

 and is lost. If, on the other hand, germ cells of species of related 

 groups meet, they may prove compatible and result in the production 

 of what we call hybrids, traceable, we believe, to the unstabilized 

 microchemical composition of the contents of the germ cell. 



In the Pyramidellidae, Cerions, and Goniobasis mentioned, the hy- 



