8 
found to be feebly endeavoring to burrow into the mud, The water 
in the pools from which these dying fish were taken registered 43°F. 
and 44°F. Some of the dying fish revived when brought to the 
laboratory and were kept for several weeks before being preserved. 
While temperature apparently explains the migration inland and 
the subsequent return to the salt water, it is interesting to note that 
during a period of two or three weeks in August, during the past sum- 
mer, the fish did not migrate to the shallows. This condition may 
not be in evidence every year, but some data indicate that it is the 
usual thing. Records taken by Mr. F. E. Mehrhof at Bonhamton 
in late July and early August showed that the killifish were very 
scarce at that time. Mr. Russel Gies, chief inspector of the Union 
County Mosquito Extermination Commission reported that during 
the period between August 4 and August 10, the fish did not run 
into the ditches and could not be attracted into them by meat baits. 
While the meat bait probably caused acids of decay which would 
drive the fishes away, the fact that there was no migration for at 
least a week seems important. Records from other inspectors through- 
out the State showed that there is apparently a period of about two 
weeks in August marked by almost complete absence of the actively 
feeding killifishes from the marshes. 
Among the explanations which occur to me the following im- 
portant ones will be further discussed elsewhere. First, the tempera- 
ture of the water may be sufficiently high to reverse the reaction of 
the fish to fresh water and cause it to return to salt: second, the 
exhaustion subsequent to spawning may cause the fish to hesitate 
about wandering with the tides; third, appetite may be satisfied in 
the case of a large body of fish which have been living in brackish 
water and which begin to return to the salt, to be replaced by others 
which have not been far inland. These points will be taken up in 
detail on page 10. 
Some of the finest experimental work on fishes has been done 
by Dr. Victor E. Shelford (12) of the University of Illinois and his 
students, Dr. W. C. Allee and Dr. M. M. Wells. Much of the dis- 
cussion on migration to follow is based on their findings. 
Shelford and Powers have shown (12) that herring are sensi- 
tive to temperature differences as small as 0.2°C. 
Johnstone (4) has shown that the migration of herring in Eur- 
ope is closely associated with the salinity and temperature of the sea. 
Shelford and Powers (12) have shown that alkalinity and acidity 
are more important than salinity. The herring and salmon experi- 
mented with reacted to small fractions of a cubic centimeter per 
liter of HeS and became negative to sea water which was slightly 
more acid than the fresh. 
Wells (16, 17, 18, 19) takes issue with Marsh who claims that 
“water which will support life must be slightly alkaline.” Wells 
claims (18, 19) that the water which seemed slightly alkaline when 
