52 INLAND FISHERIES. 



Wliere tlie curve is steep, the g-rowtli is rapid ; where it is on the 

 level, there is no growth. 



It will appear at ouce from the curve that the growth continued 

 rapidly through the fall and early winter, /. e., between October 2d 

 and January lltli. 



After the January measurement the growth becomes slow and 

 continues slow until the first of August. This is the period of the 

 growth that is of particular interest, for the slow growth continues 

 not only through the cold months from January to April, but 

 through May, June (June being the month of least growth), and 

 a part of July. In August the rapid growth begins again and 

 continues, in the warm and cold months alike, up to December. 



It is evident, therefore, that the temperature of the water does 

 not to any very great extent determine the rate of g-rowth of the 

 scallop. 



Cessation of growth and its relation to the hreeding-season. — It has 

 already been stated (p. 48) that the sexual products develop in 

 the body of the scallop during- the winter and spring. In May 

 the glands are distended Avith eggs, and in June nearly all the 

 eggs are laid. There is, therefore, a striking correspondence be- 

 tween the slow growth from January to July and the develop- 

 ment of the sexual products. As soon as the spawning-season is 

 past the rapid growth heglns again. 



Line of growth.— 1m old scallops there is a plainly marked line 

 running across the shell, parallel with the margin, which is called 

 the line of growth, and upon it the fishermen base their judgment 

 of the age of the scallop. What is the explanation of this line, 

 and what does it signify? It has l)een shown in the case 

 . of the clam that the similar lines of growth do not indicate the 

 age of the individual, but are due to the accidents in the life of 

 the clam when the margin of the shell is injured — as by burrowing 

 in gravel. Clams, therefore, which are frequently disturbed have 

 numerous lines of growth, while those left undisturbed, like the 

 one photographed an Fig, G, show none. In the scallop the case 

 is different. The usual ox3inion is that the line marks the cessa- 



