~ 2 BULLETIN OF THE BUREAU OF FISHERIES. 



Another explanation of this difference is the possibility of the existence of an in- 

 herent controlling factor in growth, whereby an average growth may be obtained by 

 the end of the second year. That is, in the case of a small first year's growth there 

 would be compensative additional growth the second year. This phenomenon is not 

 of uncommon occurrence in organisms. Barney (,1922) in studies of growth in terrapins 

 finds "runts" selected in I9 i 3 in 1917 exceeding in growth larger selected individuals 

 of 1913. 



A plant of yellow sand-shell, LampsiUs anodontoides (Lea\ was not as successful in 

 numbers, but yielded three juveniles which survived the summer, and the largest attained 

 a size of 8.3 millimeters in 6 months. The second summer it attained a length of 41 

 millimeters and a weight of 5.8 grams. 3 



GROWTH IN AQUARIA, TANKS, AND TROUGHS. 



A plant of juveniles from two bass, Micropterus salmoides, and one calico bass 

 Pomoxis sparoidcs, was obtained in a rectangular glass aquarium. The young were 

 readily found within a day or two after their escape from the fish, but later than this 

 only shells of the earliest stages could be found. It is possible that the absence of growth 

 in this instance was due to the destruction of the young mussels by enemies to be men- 

 tioned later. 



Another test of the possibilities of aquaria was made by placing in them rapidly 

 growing mussels taken from the floating crate at a more advanced stage and comparing 

 their growth with the growth of mussels remaining in the crate. The growth in milli- 

 meters and the increase is shown in Table 4. While in the aquarium the same individuals 

 were measured each time, the measurements of growth in the crate were not based 

 upon particular mussels, but upon different examples taken as representative of the 

 lot. Observations were made in this way, because the recovery of marked mussels in 

 the crate entailed danger of too much disturbance to the whole plant. 



Table 4 -Comparative Growths op Juvenile Mussels ix Aquarium and in Floating Crate. 



The figures, although only approximate, are sufficientlv accurate to represent 

 fairly the great difference in growth that has been shown in many experiments in other 

 ways. The total growth from the beginning of the juvenile stage, June 10 to August 

 17, is 7 millimeters for the largest of three mussels placed in the aquarium for three 

 weeks, while it is 10. 1 for the smallest of three taken from the crate on the same date. 

 This gives a difference of 3.1 millimeters where the influence of the aquarium is exerted 

 only for the relatively short period of three weeks. 



'Attention is called to the employment of thegarpikes, Upisostos osseus (L.)and L. i,hto«„ mu s Raf. . as hosts for the mussels 

 m th.s expenment. These are the only fish found of many tested which wil. carry the giochidia of this mussel (Howard." T 4 b)" 



