OF MASSACHUSETTS. 71 



again less so. Nassa possesses an extremely weU-developed sense for 

 finding food and gathers around the scallop in numbers. Then a con- 

 certed action takes place, whether intentional or by accident, but it 

 occurs time and time again. One Nassa forces itself between the valves 

 of the unwary scallop, which at once close with a snap, but only part 

 way, as the little winkel has formed a wedge between the valves which 

 permits the entrance of more of its kind, which rapidly fall to eating 

 the contents (Fig. 94). "While we cannot attribute this mode of 

 attack to any reasoning powers of the small creatures, the fact remains 

 that 17 out of 500 scallops, confined in a pen 10 feet square, in two 

 weeks' time were killed in this way. However, under natural conditions 

 this would be impossible in the open. The scallops were observed c6n- 

 tinually to fiirt off the crawling Nassa by snapping the valves, and in 

 this way were able to protect themselves. 



(d) Passive Enemies. — The scallop has besides these active enemies 

 other passive foes which perhaps do not accomplish so much apparent 

 damage but affect the growth of the animal and in some cases result 

 in its death. Such are the enemies which use the same food and retard 

 the growth by depriving the scallop of sufficient nourishment. All 

 other shellfish, both valuable and of no importance, come under this 

 head. Another class of passive enemies are the ectoparasites on the 

 scallop shell, the sea weeds, such as Enteromorpha, Ulva lactuca, etc., 

 barnacles, Serpula (worm tubes), Anomia, Crepidula, oysters from 

 one to two years old, Acmsea, etc., which not only partake of the same 

 food but hinder the movement through the water, and in cases like 

 the oyster and serpula, by their growth in time kill the scallop, in the 

 case of the former by weight of shell, with the latter by binding edges of 

 the valves together. 



(e) Man. — While the main cause of the decline of the natural clam, 

 quahaug and oyster beds is overfishing by man, the decline of the scallop 

 fishery cannot be so considered. The scallop has a short Hfe, hardly 

 25 per cent, passing the two-year limit; so it does no harm to capture 

 the marketable scallops which are over sixteen months old, as the scallop 

 spawns when one year old and dies a natural death usually before it 

 reaches a second spawning season. When only old scallops are taken, 

 as is generally the case, it is probably impossible for man to exter- 

 minate the scallops by overfishing. Unfortunately, in certain localities 

 in the past there has been a large capture of the " seed " scallop, viz., 

 the scallop less than one year old, which has not spawned. This has 

 worked the ruin of the scalloping in these localities. The capture of 

 the spawners for another year merely makes the next year's set so 

 much smaller, and causes a rapid decline. 



As a rule, it is hardly profitable to catch the " seed " scallop, owing 

 to its small size. But a direct relation can be established between a 

 high market price and the capture of seed. When the market price is 



