OF MASSACHUSETTS. 67 



eyes, so far as concerns the gross anatomy, closely resemble those of the 

 higher animals, and are connected to the circumpallial nerve by short 

 nerve fibers. To what extent the animal can see is a question. Observ- 

 ers have stated that scallops lying on the eel grass notice a person 

 wading through the water and swim off. Whether this is due to sight 

 or to the disturbance of the water is uncertain. It is true that move- 

 ments in the water have more effect than those outside, and the effect of 

 shadows on the scallop may cause it to withdraw its tentacles. The 

 approach of enemies is readily recognized by the scallop, which scuttles 

 out of harm's way. Whether this is from sight or other modes of sensa- 

 tion is as yet undetermined. 



Yeliger scallops apparently are not sensitive either to dark or light. 

 With scallops of 2 millimeters and over, in which the eyes or tentacles 

 are developed, different results were obtained. A few tests were made 

 with animals of this size in small dishes, covered with black paper, 

 except in certain places for the admission of light at the will of the 

 operator. Many of the results were negative, but a slight heliotropic 

 (toward light) tendency was evidenced. 



The young scallop under 3 millimeters evidences little preference for 

 different colors. Tests along this line have given negative results, as 

 the distribution on areas of different color seemed at random. 



Scallops will live in waters that have a density of 1.010 or greater, 

 one-half salt to one-half fresh. This has been tested by observations in 

 different localities and by keeping the animals in aquaria with various 

 densities. The scallop, compared with the clam and quahaug, succumbs 

 more readily. In aquaria, where these burrowing mollusks will live 

 indefinitely, it is often difficult even with running water to keep the 

 scallop alive for more than two to three weeks. 



ENEMIES. 



Owing to its free life and activity the scallop is beset by relatively few 

 enemies, as compared with the oyster, or, more properly speaking, 

 suffers less destruction from the same adversaries. Nevertheless, there 

 are certain species which prove dangerous and cause the scallop a con- 

 tinual struggle to maintain its existence. Naturally in the early life 

 of the scallop the destruction is much greater, and it is necessary to 

 divide the enemies of the animal into two classes: those which menace 

 (1) early life; (2) adult. 



Enemies of the Young Scallop. In the early life of the young scallop 

 it is not so much the active animal enemies as the adverse natural 

 conditions that destroy the embryonic larvae. When the fact that only 

 one of the several million eggs liberated by the adult spawning scallop 

 ever reaches maturity is considered, the extent of the destructive powers 

 of nature becomes strikingly manifest. The early life of the animal is 

 the critical period of its existence, and it is at this point that the young 



