The Relation of Shellfish to Fish in Oneida Lake 25 



fins, or tail, and upon which the young clam immediately 

 fastens itself. On this fish or other host the young clams 

 become imbedded in the skin, which entirely covers the 

 mussel embryo. After the lapse of a certain time (varying 

 from nine to 74 days in different species) the young, having 

 completed their transformation, break the cyst and fall to 

 the bottom, usually shaped, though very small, like mature 

 mussels. There are therefore four distinct stages in the 

 growth of a mussel: 1, the fertilized egg; 2, the glochidium 

 living in the brood pouch of a mussel; 3, the parasitic stage, 

 encysted in the skin of a fish or salamander; and 4, post- 

 glochidial development, with fully formed shell. Subse- 

 quent growth is principally in size. Unless the young mussel 

 drops from the fish to a suitable habitat it will not long 

 survive. A rocky or pebbly bottom seems to be the most 

 favorable to the growth of the young mussel and it is also 

 upon such locations that many adult clams are found. 



Several interesting facts are now known concerning the 

 subject of mussel propagation. Two principal kinds of young 

 or glochidia occur: one, hooked, the other bookless. The 

 former attach themselves by these hooks to the fins or other 

 external parts of the fish, while the latter become encysted 

 in the gills of the fish. It is believed that the hookless type 

 are fixed to the gill by a fluid produced by the irritation of 

 the gill by the young clam. 



It has also been ascertained that there is a long and a short 

 period of reproduction, the former having the eggs fertilized 

 from the middle of July to the middle of August and the 

 glochidia being carried in the brood pouch until the follow- 

 ing spring or early summer. In the short period the entire 

 breeding season is confined to about four months, extending 

 from the end of April to the middle of August, and the 

 glochidia are discharged as soon as they are fully developed. 

 The clams of Oneida Lake represent both long and short 

 periods, two species of clams representing the latter and 

 13 the former period. 



This relation between fish and mussels is very significant 

 when we remember that such fish as the bullheads and other 



