436 Biology in America 



in the gills of the mussel which hang in sheets between either 

 valve of the shell, and the internal organs. Here they grow 

 until they attain what is known as the glochidium stage, 

 when the young mussel possesses a shell of its own, with 

 paired valves. They are now set free in the water, and 

 slionld they be so fortunate as to come in contact with cer- 

 tain speeies of fish, chiefly those of the sunfish family, 

 they attach themselves to the gills or tins by means of 

 their valves and force the fish to become their foster 

 parents. The food of the young mussel at this stage is 

 obtained from the tissues of the fish whi.-h acts as foster 

 parent, in which they become embedded', living as parasites 

 upon the latter. After ten to forty ^~ days of this indolent 

 existence, during which time the glochidium is metamorphosed 

 into a mussel, it drops to the bottom of the river or pond 

 and burrowing into the mud or sand, proceeds thereafter 

 to find a living for itself. This it does by means of a tube 

 or siphon, which it thrusts up to the surface of the river bed, 

 from the bottom of its burrow, and through which there 

 circulates a stream of water carrying in oxygen, and food 

 in the form of minute plants and animals or finely divided 

 bits of organic matter of any sort, and carrying out carbon 

 dioxide and other wastes. 



The task for the mussel culturist then is to secure the 

 glochidia from the gravid mussels ^nd find foster parents 

 for them. This is done by placing the young glochidia 

 obtained from the mussels in tanks containing the proper 

 number of fish of the right species to carry successfully the 

 number of glochidia provided. The extent of infection by 

 glochidia which any given fish can stand is a matter of 

 importance, for if loaded too lightly, there is a waste of time 

 and effort in securing more fish than necessary, while if 

 loaded too heavily the fish may not survive the strain put 

 upon it, and both fish and glochidia are lost. The optimum 

 number of glochidia varies for different species of fish. A 

 young bass or sunfish, three to four inches long, will carry 

 successfully as many as 1,000, a number which will kill many 

 other species. 



Our knowledge of the life history of the mussels is largely 

 the result of the investigations of Curtis and Lefevre at the 

 University of Missouri. Their studies have been continued 

 and amplified at the Bureau of Fisheries station at Fairport, 

 Iowa, where the practical propagation of mussels has been 

 conducted for several years. In 1918 fish carrying more 

 than 200,000,000 glochidia were set free, but no definite facts 

 of mussel increase as a result of the work are yet available. 



" In one case a period of six months has been recorded. 



