NOVEMBEK 15, 1912] 



SCIENCE 



679 



tion and experiment, that the contradictory 

 evidence brought forward recently by Pearse* 

 seems at first sight enigmatical. However his 

 discovery of frog larvas in three pools of an 

 estero, or small creek opening into Manila Bay, 

 is capable of explanation although, because of 

 osmotic difficulties, it is impossible to carry out 

 the necessary experiments quantitatively on 

 forms which do not live equally well in fresh 

 and salt water. 



pronounced, and came on more quickly than 

 in the weaker. Death resulted, therefore, prob- 

 ably more from dehydration than from the 

 specifically poisonous effects of the NaOl. 



These results led to an attempt at accli- 

 matization by successively halving the .85 per 

 cent, solution, until only one sixteenth its 

 original strength. With this three series of 

 tests were begun, involving fifteen larva. The 

 results are given in tabular form as follows: 



After 32 21 



in NaCl .053125 .10625 



there were 15 14 



Time of acclimatization 101 hours. 



Average strength of preparatory solution .199 per cent. 



The three analyses reported by Pearse are 

 not strictly comparable, and in the calculation 

 of the jSTaOl from the total CI no standard of 

 reference is given, nevertheless it follows from 

 recalcxilation on the basis of Forchheimer, that 

 the solutions dealt with must have been, as 

 stated by Pearse, roughly, 2.6 per cent., 2.1 

 per cent, and 1.1 per cent. NaCl respectively. 



As the larvae were found in a tidal area 

 where fresh and salt water meet, it is not prob- 

 able that they were exposed, continuously dur- 

 ing their development to the amounts of NaOl 

 given, but it is probable that they .developed in 

 a medium never free from this salt, and that 

 despite the fact that .6 per cent, is ordinarily 

 sufficient to prevent gastrulation. 



Acclimatization to Osmotic Pressure. — ^A di- 

 lution of .85 per cent. NaCl (.25 per cent, less 

 than the weakest solution reported) causes the 

 death of 87 per cent, of the larvffi of Rana 

 pipiens exposed to it for eighteen hours, 

 whereas a solution of twice this strength kills 

 97 per cent, in three hours, and is therefore six 

 times more fatal than the weaker solution. 

 This fatality, however, depends on osmotic 

 pressure, for both solutions brought about 

 shrinkage, and an associated slowness and 

 feebleness of reaction to touch. In the 

 stronger solution these symptoms were more 



^ Pearse, A. S., ' ' Concerning the Development of 

 Frog Tadpoles in Sea Water," Fhilippine Journal 

 of Science, Vol. VI., No. 4, Section D. 



' ' ' Dynamics of Living' Matter, ' ' p; 47. 



From control observations I found that 24 

 hours is just about the limit of endurance in 

 the .85 per cent, solution, whereas without 

 acclimatization 18 hours is the limit. Life, 

 therefore, can be prolonged one third by a pre- 

 liminary slow passage through weaker solu- 

 tions. From this I conclude that the ability 

 of amphibian larvse to exist in sea water de- 

 pends on their not being introduced into the 

 stronger solutions too suddenly. This de- 

 sideratum can certainly be fulfilled in an 

 estero. These experiments leave entirely open 

 the question of racial acclimatization which 

 is probably of great importance. 



The Antagonistic Ejfecis of Calcium. — As 

 Loeb^ has repeatedly pointed out, very small 

 quantities of Ca suffice to antagonize the 

 poisonous effects of NaCl. Thus he found 

 that in 100 e.c. of 5/8 M NaCl the eggs of 

 Fundulus failed to develop, whereas when he 

 added 4 c.c. of an M/64 OaSO, solution, 75 

 per cent, of the eggs formed embryos. From 

 this it follows that one molecule of CaSO^ is 

 sufficient to antagonize 1,000 molecules of 

 NaCl. It does not of course necessarily fol- 

 low that this will prove true with other or- 

 ganisms, nor must we forget that other ions 

 have been shown to antagonize the Na, but 

 the antagonism of the Ca against the Na is 

 so strong in the case of Fundulus that it is 

 only natural to try this first in the case of the 

 frog larva. 



