82 BULLETIN OF THE BUREAU OF FISHERIES. 



The floating crate method furnished an unusual opportunity for the study of living 

 juveniles after the first two weeks, but as it was the first successful trial, for fear of dis- 

 turbing the plant, the occasions for raising of the baskets were reduced to a minimum. 

 Such incidental notes as were taken while tending the cultures may be of interest, 

 inasmuch as so few observations have been made upon the habits and habitat of the 

 juvenile Naiad. 



In relating observations upon the habits of the culture attention is directed to the 

 conditions prevailing during the experiment. The arrangement of the crate and baskets 

 is described under Methods, page 64. (See also figs. 74 and 75.) The crate, being placed 

 in the river channel, received a current of 2 to 3 miles per hour. In the individual 

 baskets when at the surface no current could be detected. The fineness of the mesh 

 was chiefly responsible for this. Much of the time, however, owing to a slight sinking 

 of the crate, water to the depth of an inch flowed over the top. Thus the mussels, 

 although probably never in a continuous current comparable to that in the river, 

 received a constant renewal of the water supply. A gathering of the mussels at the sides 

 of the basket was very marked. This might be construed to indicate that they found 

 there conditions more favorable than at other points. Doubtless at the bottom of the 

 basket the freshest supply would be at the outer edges. During a greater part of the 

 summer flood conditions prevailed in the river, so that the content of suspended silt was 

 very high. The checking of the current on reaching the baskets resulted in the deposit 

 of this silt at the rate of over 1 inch per week. This is considerable when the conditions 

 are considered. Thinking this might bury the young mussels, the silt was removed 

 weekly by washing through the sides of the basket. Later this regimen was abandoned, 

 being considered too violent and an unnecessary disturbance for the minute mussels. 

 At the end of the season in November the silt in the bottom had accumulated to a depth 

 of 3 inches. This sedimentation, however, covered a long period, most of which was not 

 in time of high water. 



The first collection of Lampsiles luteola from the crate numbered 7 at an age of 15 

 days. Three of these were built into the mosaic tube of a caddisfly larva, and of these 

 three, two were still alive. The larva finding a scarcity of sand grains and similar building 

 material had evidently made use of the mussels. The predacious worms mentioned 

 above as so abundant and destructive of mussels were not found in the crates. They 

 are apparently a bottom species, and thus the position of the crate on the surface fore- 

 stalls their ravages. One of the most conspicuous species associated here with the 

 mussels was the larvae of the Ephemerid mayflies. As they are vegetarian they could 

 be destructive of young mussels only in a competitive way, but ordinarily in crate culture 

 they would not develop in time to be troublesome. The presence of these and like insect 

 forms is doubtless due to the development of eggs deposited by the adult insects in the 

 crate itself. Some other forms observed were numerous Hydra and Polyzoa, together 

 with the free-swimming forms which make up the plankton of the main river. 



The byssus was first observed in mussels of 38 days. The attachment was to such 

 objects as could be found in the mud at the bottom of the baskets, some on the filaments 

 of Cladophora and other algae growing in the basket. One was found attached to the 

 tarsus of a dead spider. The byssus increased in diameter and length with the growth 

 of the mussels. When the latter were large enough to be readily seen, it was surprising 





