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Show 1938] Jones: Experiments on the Snail, Discus alternatus (Say) 117 served to repair the same as follows: 6 had finished the repair completely by the end of the first week; by the end of the second week 7 more had completely finished, while all had started repair within four weeks. Simi larly, in May and June 1932, three shells of 18 mm., 12 mm. and 10 mm., greatest diameters respectively, successfully repaired breaks of the apical whorl in one week by vacating the broken whorl and sealing it off with a partition. Variously notched apertures were easily repaired by other indi viduals. Others showed themselves capable of replacing a small portion broken out of the whorl next above the body whorl. if the area were not too large. In the case of the snails seemed to be unable to move the mantle large areas, forward over the slit, hence they were retained far back in the shell. I believe they eventually starved. The hardest breaks to repair were the long narrow slits and windows cut in the body whorl of the shell. In this case the body of the snail would emerge through the slit or window. which sition handicapped the snail in many ways. and in po led to peculiar Repair material is very brittle and apparently different from regular shell structure. The supply of repair material is evidently limited as snails die, perhaps of exhaustion, when con tinued repair is required because of repeated breaking of _reconstructed shell material. As all my observations on regeneration were on less than fifty shells, all should be regarded cautiously until verified. Finally three experiments were performed attempting to isolate tempera ture, atmospheric pressure. and humidity factors which might affect shell formation. In order to conserve space all data on these experiments are given in chart form, together with a picture of the "set up" of the apparatus instead of description. Experiment 1, as charted, actually divides itself into two experiments, running simultaneously, as follows: flasks 1, 2, and 3, a temperature experiment at atmospheric pressure and 100% relative humidity, with out-of-door temperature (flask 1) fluctuating, and indoor temperatures (flask 2 and 3) remaining approximately at 11.5 degrees C. (room tempera ture) and 37 degrees C. (oven temperature) respectively. Flasks 3 and 4 a present pressure-experiment at approximately constant temperature and hu midity, but with the former at atmospheric pressure, and the latter at a re duced pressure capable of supporting an 11-inch water column. The tempera ture experiment indicates that the 11 degree constant temperature, and per haps the varying (-30 to 300 C.) outside temperature are in this case the more favorable for shell growth. The higher oven temperature killed off most of the individuals. Certain histological changes in the survivors have been described in "A comparative study of certain goblet cells" (Jones 1937, as above, p. 8, also fig. 6). Activity was also noted in this experiment as indicated on the chart of Experiment 1. Activity was greatest in flask 2 at 11 degrees C. Interesting, but as yet unexplained, clustering behavior prepara tory to burrowing at low temperatures was noted in flask 1. Details and comparative notes on burrowing in this species and in several Utah species have been presented in "Burrowing of snails" (Jones, 1935, as above). We have several previous accounts of the interesting phenomenon of clustering. Lind in 1895 in Nautilus records in Miami County, Ohio a cluster of 125 shells all cleaned out by some unknown agency, 112 of these were Polyqyra e.levata, 9 were Discus aliernatus, the others being of three other species. This may not have been a natural aggregation. Higgins (Surface, H. A. 1890. A descriptive catalogue of the shells of Franklin County, Ohio, Part I, Land shells. Ohio Agric. Exp. Sta., May 1890) is quoted as finding nests con taining as much as a gallon and a half of P olygyra multilineata (Say). Van Hyning (Van Hyning, T., 1904. A molluscan stampede, Nautilus, Vol. 18, No.3, p. 31) reports a "stampede" of Phvsa gyrina, evidently clustering in a cold spring in a crayfish hole at Des Moines, Iowa in the summer of 1899. deformations in reconstruction of the shell. some cases |
