No. 625] SHORTER ARTICLES AND DISCUSSIOX 



183 



at 41.5°. There is thus seen in fundulus the correspondence 

 usually found in every thermal species between the temperature 

 at which the animal lives and the maximal temperature which 

 it can successfully withstand (cf. Mayer, '14). 



The alkalinity of the waters inhabited by the Bermuda fun- 

 dulus is quite various. In the mangrove creeks the reaction of 

 the water along the shore may vary a little with the state of the 

 tide, but is usually not far from p// = 8.1. In the landlocked 

 brackish ponds, however, the alkalinity is commonly much higher 

 than this. In one pond, where many algae were growing, the alka- 

 linity was conspicuously high, p//^ 9.0-9.2 (except after 

 rains) f and in another, with a sparser growth of Avater plants, 

 the reaction usually observed was pji = 8.1. Rain water had at 

 this time a consistent reaction of 5.9-6.0, but after contact 



with the soil and limestone it quickly becomes alkaline, so that 

 the water in cave pools, or dripping from growing stalactites, 

 was found to have a reaction of = 7.9-8.0. The high alka- 

 linity of the pond waters may be important in determining the 

 survival of fundulus in abnormal solutions. 



If the idea is correct that the composition (e. g., the calcium 

 content) and (?) the temperature of the sea water or pond 

 water are responsible for the high resistance of the brackish- 

 pond fundulus to concentrated sea water, then avc sliould expect 

 that NaCl solutions would ho less toxic for the Konnuda fundu- 

 lus than for the northern vnrirty. which. ;icco!'(liii<i- to Loeb, and 

 Wasteneys ('12), is killed by 1 M XaCl in less than one half 

 hour (at about 18°-20°, it is inferred). The pure NaCl solu- 

 tion increases the permeability of the surface membranes of 

 fundulus. At 25°-27°, 50 per cent, of the Bermuda fundulus 

 lived forty-five minutes in 1 M NaCl solution, when the speci- 

 mens were taken from the mangrove creeks. Individuals from 

 the landlocked brackish ponds lived about the same length of 

 time (even after rapid washing, three times, in changes of NaCl 

 solution). At 20° they lived a little longer. This result is in 

 agreement with that obtained experimentally by Loeb ('16, p. 

 332), namely, that fundulus adapted to higher concentrations of 

 sea water became more resistant to pure NaCl solutions; those 

 brought artificially to live in i% 31 sea water could live two to 



green alga Valonia. 



