46 American Fisheries Society 



they may be divided, very roughly indeed, into two great 

 classes which are spoken of as short-term breeders and 

 long-term breeders. With the short-term breeders, the 

 early stages of the life-history are completed with great 

 rapidity, the eggs are matured and incubated, and the 

 larvae, or "glochidia," hatch, and, after entering into a 

 state of parasitism on fish, metamorphose into free-living 

 young mussels all within the brief space of a few weeks 

 or months of the summer season. With the long-term 

 breeders, on the other hand, the completion of the cor- 

 responding stage of life-history extends over portions of 

 two calendar years: the eggs are matured in the first 

 summer, while the period of incubation extends through 

 the winter and into the following spring. Late in the 

 spring or early in the second summer, the larvae, or 

 "glochidia," become parasitic on fish to complete the met- 

 amorphosis and the young mussels enter upon a free-liv- 

 ing career at the age of a year, more or less, from the 

 time of maturity of the eggs. They soon begin, how- 

 ever, to make up for lost time; for it is an interesting 

 and remarkable fact that the long-term breeders are rela- 

 tively rapid growers, while the short-term breeders are 

 very slow in later growth. The quickness of the latter 

 class ends with the start. Familiar representatives of 

 the long-term class are the mucket, fat-mucket and yel- 

 low sand-shell, which may attain a market size in four 

 or five years; the niggerhead, pimple-back and blue- 

 point, of the short-term class, require a considerably 

 longer period to become of a substantial size. 



Several species of long-term breeders are those which 

 have proven best adapted for artificial propagation. It 

 is as yet doubtful if propagation measures can be applied 

 with practical success to the very valuable mussels of 

 the short-term breeding class. 



Assuming then that we shall continue to have propa- 

 gation without protection, we must look for the follow- 

 ing result : The mussels of the more rapid growing spe- 

 cies may be continued in the particular waters to which 

 they are adapted and where they may be propagated with 



