OF MASSACHUSETTS. 87 



Age and Growth. — With the exception of the winter months (De- 

 cember to May), during which no growth takes place, the scallop con- 

 tinues to increase in size until its death. The proportionate growth as 

 determined by the volumetric increase steadily diminishes after the 

 period of first shell formation (the veliger or embryonic shell) . On the 

 other hand, the actual gain in inches or millimeters is approximately 

 constant for the first summer, then slowly decreases during the second 

 and even third, provided the animal lives bej'ond the two-year limit. 

 The point is well illustrated by the following experiment: scallops of 

 the 1904, 1905 and 1906 sets were suspended in wire cages under simi- 

 lar conditions from a raft at Monomoy Point for a period of fifty- 

 three days during the summer of 1906 (Kg. 86). The smaller 

 (younger) scallops showed a greater capacity for growth both in actual 

 increase and in volume. The 1904 set gave an actual increase of 2.10 

 millimeters in height, or 112 per cent, in volume, a return of less than 

 1% bushels for every bushel planted; the 1905 set 3.94 millimeters 

 in height, or 125 per cent, in volume, a return of 1% bushels; the 1906 

 set 10.86 millimeters in height, or 309 per cent, in volume, a return of 

 over 3 bushels. Prom these figures it is evident that the " seed " (1906 

 set) gave about twelve times the growth in volume of the yearlings 

 (1905 set), and twenty-five times the growth of the 1904 scallops, which 

 had lived beyond their allotted life; and that there is a successive de- 

 crease, both numerically and volumetrieally, in the rate of growth with 

 the aging of the scallop. 



Environment and Growth. — Two great factors influence all animal 

 and plant life, — heredity and environment. In the case of the scallop, 

 environment seems to possess the greater influence on the variation 

 of the species, as varieties are more dependent upon the natural sur- 

 roundings than upon hereditary characteristics. By environment is 

 meant the natural conditions within which the animal lives, and which 

 determine its struggle for existence. The question of food, enemies, 

 exposure, protection, situation in large or small bodies of water, in or 

 out of tidal currents, temperature, etc., are all factors influencing to 

 a more or less extent the life and habits of the scallop, making it large 

 or small, heavy or light shelled, firm or poor meated, etc. Particularly 

 with marine animals does environment largely determine size, shape, 

 habits and rate of growth. 



With many aquatic animals larger specimens of the same species are 

 found in the great bodies of water than in the small, showing that the 

 area of water, either by a more plentiful food supply or in other ways, 

 determines the general size. Looking at the matter from a different 

 standpoint, that of current, it seems that scallops which have the greater 

 amount of water passing over them (which can be compared to resi- 

 dence in a larger area) are larger and of faster growth than the scallops 

 which do not have the same volume of water. 



