CULTURE OF FRESH-WATER MUSSELS. 87 



was successful in finding a very large percentage of marked mussels months and even 

 over a year after planting. It will be noted that his work was done in small rivers 

 where collection was possible by wading during low water. 



Solution of some of the problems still unsolved can doubtless be more directly and 

 economically reached by further investigations of the life history and habitat of mussels 

 and especially of the early juvenile stage. A few of the recent studies along these lines 

 not mentioned in the foregoing pages follow: Allen (1914, 192 1) has made a study of 

 the food of lake and river dwelling species. Baker (19 16, 1918) has made extensive 

 ecological investigations in Oneida Lake. The author has had the opportunity of making 

 an ecological survey of a portion of the Mississippi River, where mussels are abundant. 

 A report is in preparation putting forth the results of this study of conditions control- 

 ling the development of mussel beds and the growth of mussels under such an environ- 

 ment. In general, much more detailed information is required concerning the various 

 elements in an environment favorable to the mussel (see Coker, Shira, Clark, and 

 Howard, 192 1), including water content, as substances in solution and in suspension, 

 both food and gases; temperature variations; depth and flow; amount of light; and kind 

 of bottom. 



That the conditions favorable to juveniles sometimes differ from those for adults 

 has been indicated. If this is the case, as it is well known to be for many animals, a 

 more complete knowledge of the requirements of the critical postparasitic stage in 

 mussels will certainly contribute to their culture. Perhaps the most pressing problem 

 is the securing of a complete knowledge of their enemies and means of combating these. 

 There are still some commercial species for which the appropriate host is yet undeter- 

 mined, and in most cases where the host has been determined practically nothing of the 

 manner of infection and like ecological relations is known. The solution of these 

 problems is difficult because dependent upon the observation of phenomena occurring 

 in a medium different from our own. In the case of river mussels this medium owing 

 to turbidity is not readily penetrated by sight. In spite of such difficulties, however, 

 we must agree with Lefevre and Curtis (19 12) that among invertebrate animals the 

 Unionidae, for the variety in economic and scientific interest of the problems they 

 present, are scarcely excelled. 



LITERATURE CITED. 



Allen, William Ray. 



1914. The food and feeding habits of fresh-water mussels. Biological Bulletin, Marine Biological 

 Laboratory, Woods Hole, Mass., Vol. XXVII, No. 3, p. 127-146, 3 pis. Lancaster. 



1921. Studies of the biology of fresh- water mussels. Biological Bulletin, Marine Biological Labora- 



tory, Woods Hole, Mass., Vol. XL, No. 4, p. 210-241. Lancaster. 

 Baker, Frank Collins. 



1916. The relation of mollusks to fish in Oneida Lake. Technical Publication No. 4, New Vork 

 State College of Forestry, Syracuse University, Vol. XVI, No. 21, p. 1-366, figs. 1-50. 

 Syracuse. 

 1918. The productivity of invertebrate fish food on the bottom of Oneida Lake with special ref- 

 erence to mollusks. Technical Publication No. 9, New York State College of Forestry, 

 Syracuse University, Vol. XVIII, No. 2, p. 1-253, figs. 1-44, 2 pis. Syracuse. 

 Barney, R. L. 



1922. Further notes on the natural history and artificial propagation of the diamond-back terrapin. 



Bulletin, U. S. Bureau of Fisheries, Vol. XXXVIII, 1921-22, p. 91-111, figs. 76-84. 

 Washington. 



