7° BULLETIN OF THE BUREAU OF FISHERIES. 



On consulting the temperature averages the assumption is natural that such growth 

 as occurred took place before the temperature fell. 



It is obvious that for the whole period (Oct. 20 to Nov. 20) growth was much less 

 than in the warmer months. Compare the maximum of 0.5 millimeter for the period 

 with the growth of 4.9 millimeters shown in Table 1 (p. 69) for the period from Sep- 

 tember 12 to October 10. The desire to secure these records resulted in the postpone- 

 ment of the date for removal from the river until a time dangerously late. On the 

 night of November 19 ice floes bore down on the crate. Only by the rarest good fortune 

 was the whole plant saved. The ice instead of destroying the crate or carrying it away 

 landed it on shore, where the mussels were extricated without injury. A count of 

 mussels grown in the basket follows: 



Alive in basket Nov. 20 „ a 



Dead in basket Nov. 20 6 



Removed from basket June 25 to Oct. 30 -r 



Total living for season 3l - 



As the original plant from the three surviving bass was an estimated 2,400 juveniles, 

 it would give a survival of something better than 8y$ per cent. The mortality would 

 be indicated by the difference in the figures of the original plant and the final crop. 



Observations upon growth were continued during the second and third summers. 

 The results of measurements taken from month to month on marked mussels are 

 indicated in Table 3. In figure 71 is plotted the increase of growth per month for 18 

 months, with the graph of the average water temperature. The data are taken from 

 observations on mussel No. 3 in Table 3, as the record for this mussel is the most 

 complete. Absence of growth from November to the middle of April, though not shown 

 in the table, was observed and is supplied in the graph. Lack of observation for May, 

 19 15, is supplied from another brood of the same age giving an approximation to the 

 true figure sufficiently close for our purpose. This would give the following increases 

 in millimeters for each month: May, 1.7; June, 6.1; July, 9.1; August, 7.1; September, 

 3.9; October, 1.5 ; May (1916), 1.9. The growing season seems obviously to be correlated 

 with the rising temperature of summer. In a general way, doubtless, it is dependent 

 upon the phytoplankton, and the plankton is controlled to a large degree by the tem- 

 perature (Kofoid, 1903, p. 572, par. 18). 



Table 3. — Growth op Mussels in a Floating Crate in the Second and Third Years. 



1 No growth indicated here. Decrease perhaps due to breaking of periostracum. 



