124 GEORGE G. SCOTT. 



the time with the question as to the percentage of Fundulus that 

 survive transfer to fresh water. The experiment was begun on 

 March 13, 1909. On April 2, twenty days after, ten survivors 

 were removed. The total body length was taken together with 

 the length of the regenerated tissue of the caudal fin. The 

 average actual length of the regenerated tissue of the caudal 

 fin was 0.238 cm. The remaining ten survivors were removed on 

 April 16, thirty-four days after the experiment was begun. The 

 average actual length of regenerated tissue was .495 cm. The 

 temperature of the water was about 20 C. A second experiment 

 was begun on November 18, 1910. Out of thirty fishes operated 

 on and placed in fresh water on November 18, but seven survived. 

 In forty-two days during which the fish lived in fresh water the 

 length of regenerated tissue was .41 cm. Out of a lot of thirty 

 other specimens operated on two weeks later six survivors on 

 December 30, 1910, about twenty-eight days after the experiment 

 was begun, showed a regeneration of .23 cm. During the course 

 of the experiment the fishes were transferred every few days to a 

 smaller glass jar and the aquarium thoroughly cleaned and 

 replenished with fresh water from the tap. In 1908 I found 

 that the average length of regenerated caudal fin tissue of 108 

 specimens of Fundulus heteroditus in sea water at Woods Hole 

 for a month was about 0.6 cm. It will be seen that in fresh 

 water the regeneration of the first of the above lots was 0.495 

 cm. in 34 days, that of the second lot, 0.41 cm. in 42 days. It 

 appears probable that in fresh water the amount of regenerated 

 tissue is decreased but because the animal as a whole is affected 

 by fresh water. Further discussion is not proper on account of 

 the meagerness of the data. Results show that not only does 

 Fundulus survive transfer to fresh water but also that under these 

 conditions, physiological processes are sufficiently normal for 

 the regeneration of removed tissue. 



Sumner in his practice in using numbers for fishes, found that fre- 

 quently individuals died and so the carrying on of the experiment 

 was interfered with. I determined therefore to study the changes 

 in weight in Fundulus in solutions differing in density from that 

 of sea water, by keeping a record of the individual changes in 

 weight. Now since some specimens of Fundulus die sooner than 



