HEREDITY EXPERIMENTS IN VIRGINIA AND 

 WEST VIRGINIA 



By PAUL BARTSCH 

 Curator, Division of Mollusks, U. S. National Museum 



In 1 91 2 I began a series of breeding experiments under the joint 

 auspices of the Smithsonian and Carnegie Institutions. I selected for 

 my subjects land mollusks of the genus Cerion, which I transplanted 

 to the Florida keys from the Bahamas and the West Indies. These 

 experiments have given very interesting results. They show that envi- 

 ronment, as far as Cerions are concerned, produces no appreciable 

 changes in the offspring if the animals are able to exist under the 

 changed conditions. In instances in which the changed environment 

 was adverse, it produced a lethal effect and the colony in question 

 passed out. Hybridization, on the other hand, produced de Vriesan 

 mutations, and these mutations, through segregation, appear to pro- 

 duce fixation, which we hope will eventually result in speciation, 

 the establishment of new species. 



To have a check on the Cerion breeding experiments in order to 

 determine whether the results obtained thereby are of broader bio- 

 logical application or merely phenomena peculiar to the genus Cerion, 

 I have selected Goniobasis virginica, a fresh-water mollusk of the mid- 

 Atlantic drainage, as check subjects. This work was begun 2 years 

 ago, but the Potomac floods buried the cages which were placed on 

 the bottom, and thus vitiated the tests. It is for this reason that a 

 new set of experiments was started this year, in which the concrete 

 bottom of the cages was replaced by a cypress floor covered with a 

 thin layer of cement. The three cages used in each set of experiments 

 were gathered in a cypress frame and suspended some 18 inches below 

 the surface of the water by means of two metal drums. 



These cages have a yard-square bottom and a height of 18 inches. 

 The sides are made of monel metal screening, 20 mesh to the inch, 

 and the top is of the same screening, 10 mesh to the inch. Three sets 

 of three cages each are being used. One of these is placed in the spill- 

 way below the hydro-electric plant at Millville, W. Va., another in 

 the Roaches Run Bird Sanctuary, and the third set is placed at the 

 pontoon bridge at Fort Belvoir, Va. 



The material used for the experiment consisted of young specimens 

 of the year. One set was gathered above the fall line in Occoquan 

 Creek ; another at Dawsons Beach in the Potomac, south of the mouth 

 of Occoquan Creek ; and the third was taken from the Chesapeake and 



