620 NEW YORK STATE MUSEUM 



is usually just below the low tide mark and only where currents are 

 comparatively swift. In such favored localities, they often accumu- 

 late in such numbers as to touch each other, being crowded as close 

 as they can stand. These are small clams, only large enough to dig 

 beneath the surface. The swimming embryos settle to the bottom 

 both above and below this line. 



The subsequent history of their exis-tence in this restricted locality 

 just below the low tide mark is interesting. As they become older 

 and larger, they die on the surface and in their burrows from lack 

 of food. 



Beds between tide-lines are recruited only from forms which hap- 

 pen to settle in them. 



We thus have during the months of June and July a multitude of 

 small clams which have settled just below the low tide mark in 

 certain restricted localities near clam beds. They are engaged in a 

 severe struggle for existence among themselves, and, if allowed to 

 remain undisturbed, the great majority die. They are, however, only 

 in great numbers during- certain seasons. Not in every succeeding 

 year are the numbers great. Observations have not been continued 

 long enough to determine how often, on an average, we may expect 

 a " set " such as was witnessed in 1899 ^'^ certain parts of Buzzards 

 and Narragansett bays. Clam-diggers, however, generally state 

 that it occurs every third or fourth year, though, so far as can be 

 ascertained no one has observed the phenomenon closely. 



With these data, and some additional points which will be men- 

 tioned as we proceed, we may induce certain conclusions which are 

 of value in formulating" a plan for clam culture. 



I Artificial fertilization. By cutting open the sexual glands of 

 male and female and causing the sexual cells to mingle in a dish of 

 water, fertilization can be effected easily in the case of the oyster. 

 Apparently it is accomplished with difficulty in My a, but it has 

 been done, and embryos are brought into existence at the will of the 

 operator during the breeding season. But all attempts to control 

 and rear oyster embryos to the adult condition — at least in num- 

 bers — have failed. There is every reason to believe that they would 

 fail in the clam. This point, then, may be passed over as being 



