American Fisheries Society. 65 
the loss on the fry up to the time of liberation was only five 
fish out of the 65. Probably, though, the eggs themselves were 
not actually frozen. 
NOTES ON POND CULTURE. 
Science has been of practical assistance to fish culture through 
the important pathological investigations of Mr. M. C. Marsh 
on fish diseases. It has been found that fish diseases are fre- 
quently due to abnormal conditions of the water supply caused 
by superaeration, lack of aeration, or the presence of obnoxious 
gasses. Reference is had more especially to the investigations 
of the diseases of the trout. 
Another opportunity for the scientist to render practical aid 
to the fish culturist is in that branch termed Pond Culture. To 
a certain degree is involved the question of normal water aeration, 
in the lack of which has been found the cause of diseases among 
trout. 
The importance of aquatic plants in pond culture and their 
value as oxygenators is well known. Valuable papers have been 
written relevant to the subject—notably one by Mr. C. K. Green 
at the last meeting of this society. From six to ten species of 
well known aquatic plants are regarded by all pond fish culturists 
as especially desirable. During the past two years endeavors 
have been made to collect specimens of all the aquatic plant life 
at the various pond cultural stations. The superintendents have 
reported the relative value of each so far as known; of what 
specific use the desirable ones are, and the objectionable features 
of the obnoxious ones. This work has developed the fact that 
some of the common aquatic plants are not of the same sub- 
species at all of the stations and the kinds of plants most valu- 
able at one station are not so highly regarded at another. <A 
fairly desirable plant at one station may become an obnoxious 
weed at another because of its dense and exuberant growth. The 
various subspecies of one genus are not of equal value. For ex- 
ample, it has just been called to my attention by Superintendent 
L. G. Harron that a species of myriophyllum not heretofore 
used in the aquarium or in fish ponds at Washington, D. C., is 
more desirable than the common form because it holds its foli- 
age from the root to the top of the stem. Identification is await- 
5 
