1 146 BULLETIN OF THE BUREAU OF FISHERIES. 



these laws and the phenomena appeared to be complicated by physiological and 

 chemical factors of an obscure nature. In one case (the carp) it was shown that 

 the changes took place through the gills. In another paper (1907) the same 

 author confirmed the last named result by experiments with the tautog. He 

 also found seasonal differences in the osmotic phenomena and says that "these 

 differences may perhaps be due to differences of temperature but are more prob- 

 ably due to seasonal variations in the physiological condition of the animals." 



While not entering into the work in detail, such a course necessitating 

 constant reference to figures, I will give the results of a few experiments and 

 discuss the same. 



I wish to corroborate the work of Sumner as to gain in weight of Fundulus 

 heieroditus when placed in fresh water. In this case the fishes were kept in 

 separate dishes and the record of each individual fish was kept. They were 

 taken out and weighed at intervals. The percentage of gain was obtained in 

 each case and for each period. It was found that there was considerable varia- 

 tion. Thus in one experiment there is noted a gain of 13 per cent in one indi- 

 vidual, while in the case of another fish of the same lot there was a gain of 2.1 

 per cent. The average gain was 5 per cent, or if we disregard the case of 13 per 

 cent gain, the average was 4 per cent. 



But it may be questioned what right we have to throw out the case of 13 per 

 cent gain. In the first place, this is from two to six times as great as the gain in 

 each of the other cases. What is more important, however, is that it is not a 

 normal case — that is, the fish was not in normal condition, for on referring to 

 the record it is found that at the end of six hours it had turned on its side and a few 

 hours later was dead. This was true of other similar cases. Wherever there 

 was an extraordinarily large initial gain it was noted that early death took place. 

 Again, when in the course of the experiment a marked gain in weight occurred, 

 it was found that this was soon followed by death. It thus appears that there 

 is another factor'here than merely osmotic phenomena — that there is a physio- 

 logical (vital) reaction against osmotic pressures, and as death approaches, this 

 physiological reaction ceases and the phenomena following for a short time at 

 least are osmotic. 



Now what is the effect on the blood when this species of fish is placed in fresh 

 water? A familiar experiment in histology is to observe the effect on the cor- 

 puscles of distilled or tap water and of concentrated salt solutions. There are 

 distinct effects which end in the destruction of the corpuscles. But do similar 

 changes take place when the living organism (i. e., a salt-water fish) is placed in 

 fresh water? An experiment was devised whereby one lot of Fundulus hetero- 

 clitus was kept in normal sea water and a second lot in fresh water. After cer- 

 tain periods of immersion (two hours, etc.) blood smears from fishes in each of the 



