122 GEORGE G. SCOTT. 



taken by Garrey and Loeb on the one hand and Sumner on the 

 other the present author desires to publish observations on the 

 * changes in weight in Fundulus heteroditus resulting from im- 

 mersions in solutions differing in density from that of sea water. 



Fundulus heteroditus, although found in sea water and brackish 

 waters, is known at times to pass into fresh waters. Quoting 

 from Sumner, p. 56, we find, "Bean, '03, says of heteroditus that 

 it sometimes ascends streams beyond tide water" -"Smith, '97, 

 states that it is often found landlocked in ice or quarry ponds." 

 " Dr. H. M. Smith informs me that it is found permanently in the 

 vicinity of Washington, in the Potomac and its tributaries and 

 also in ponds." 



It is thus abundantly established that heteroditus is found in 

 fresh waters as well as brackish waters and even sea water. 

 This does not mean however that they will readily survive sudden 

 changes from salt to fresh water or vice versa. Sumner tried 

 the effect of acclimatization by transferring 25 F. heteroditus 

 from the sea water (sp. gr. 1.025) to fresh water reducing the 

 salinity by .001 ths, hourly. At the end of thirty days but eleven 

 were alive. From this Sumner concluded that complete ac- 

 climatization failed. Of course this is true since fourteen were 

 dead. But what of the survivors? Why was not complete 

 individual acclimatization exhibited in the cases of these? With 

 regard to acclimatization Eugene Smith, '12, says that Fundulus 

 heteroditus may be transferred from salt and brackish to fresh 

 water. They may be transferred more safely, the less degree of 

 salinity there is in the water from which they come. Further- 

 more, while very few of those transferred from salt water directly 

 to fresh survived the sudden change, an increasing number 

 survived of those gradually transferred in the course of a week or 

 two through a number of changes of water. My records show 

 that such fishes lived from four to six months up to two years- 

 one lived over three years." The above probably represents 

 the truth of the matter. It will be observed here that the above 

 writer emphasizes the suddenness of the transfer. The effect of 

 a stimulus is related to the suddenness of its onset. In fact the 

 living mechanism may be injured under too sudden as well as 

 strong stimuli. 



