May 13, 1921] 



SCIENCE 



461 



attention at the hands of physiologists and 

 students of animal behavior, and is a problem 

 which must ultimately be considered in 

 greater detail by ecologists, students of geo- 

 graphic distribution and organic evolution. 



The purpose of this note is merely to call 

 attention to the occurrence of Oammerus 

 limnaeus Smith,i normally a fresh water^ 

 species, in a peculiar and rather saline 

 habitat.^ 



In the summer of 1920 the writers visited 

 the lee Spring Craters lava field of the Sevier 

 Desert in the ancient Lake Bonneville basin 

 described in detail by Gilbert.* On climbing 

 down into the old lava vent'' of the Terrace 

 crater we were surprised to find a small 

 crustacean abundant in the small pool of 



1 We are indebted to Mr. Waldo L. Schmitt, as- 

 sociate curator of marine invertebrates in tie U. S. 

 National Museum, for the determination, of the 

 species. The specimens are in the National Mu- 

 seum. 



2 The key to the taxonomic and distributional 

 literature is furnished by Weckel's paper on the 

 fresh -water Amphiopoda of North America (Proc. 

 V. 8. Nat. Mus., 32: 42-44, 1907), and individual 

 citations need not be given here. The species was 

 first dredged in Lake Superior. It has been taken 

 near Long's Peak, Colorado, at an elevation of 

 9,000 feet; from a cool spring, Fire Hole Basin; 

 from Shoshone Falls, Idaho; Flathead Lake, Mon- 

 tana; and from the Yellowstone National Park. 

 It is reported from Fort Wingate, N. M., and from 

 the Wasatch Mountains and Salt Lake City, Utah. 

 It is impossible to determine from the records 

 whether all the localities were fresh water habitats, 

 but that it is typically a fresh water form can ad- 

 mit of no possible doubt. It has been taken from 

 the stomachs of trout from brooks near Marquette, 

 Mich. 



3 The genus Gammerus has species which occur 

 in more or less saline coastal habitats and in non- 

 saline inland waters. 



4 Gilbert, G. K., "Survey West of the 100th 

 Meridian," Vol. 3, pp. 136-144; also "Lake 

 Bonneville," Monographs TJ. S. GeoL Survey, I., 

 pp. 320-325, 1890. 



5 The lava vent is a circular tube, at one side of 

 the wide crater, about 12 feet in diameter inclined 

 10° or 15° from the vertical. It can be explored 

 for about 25 feet when progress is stopped by 

 water. 



clear water at the bottom. It was noted that 

 a number of the animals were very slightly 

 pigmented, apparently indicating that in the 

 semi-darkness of the pool they were approach- 

 ing cave conditions. In all instances, how- 

 ever, the eyes were fully pigmented. The 

 presence of the Gammerus led to the assump- 

 tion that the water was non-saline and we 

 were preparing to replenish our water hag 

 when taste showed it to be distinctly brackish. 

 A sample of the water was therefore taken 

 in a clean Mason fruit jar from which it was 

 afterwards transferred to citrate bottles for 

 shipment to the laboratory. The water had 

 a freezing point lowering of 0.410° C, indi- 

 cating an osmotic concentration of 4.94 

 atmospheres and an electrical conductivity of 

 .0138 reciprocal ohm. The hydrogen ion con- 

 centration of the water (determined electro- 

 metrically) was Ch = 0.409 X lO"" = P^T -388. 

 Analysis showed the following composition. 



Grams per Liter 



Total solids (at 110°) . . 8.5666 



Total solids (at 210°) . . 8.1467 



Total solids (ignited) s . . 7.6400 



COs^ none 



HCO37 0.2187 



Mineral Analysis 



Per Cent, of 

 Grams Total Solids 



per Liter (Ignited) 



SiO, 0.0720 0.94 



FeAAlA 0.0030 0.04 



Ca" 0.3305 4.33 



Mg 0.2560 3.35 



Na 1.9750 25.85 



K 0.3050 3.99 



01 3.4120 44.66 



SO^ 1.3260 17.36 



CO3S 0.1075 1.41 



Total 777870 TolTs 



6 There was apparently considerable organic mat- 

 ter in solution. This could easily be derived from 

 bat guano which was observed on the lava ledges 

 surrounding the pool. 



7 Carbonates and bicarbonates were determined 

 by the titrametric method proposed by Scales 

 (Science, N. S., 51, p. 214, 1920). 



s Calculated from bicarbonate data according to 

 the formula 2EHCO3 -|- heat = E.COs -|- CO, -|- H,0, 



