222 BULLETIN OF THE BUREAU OF FISHERIES. 



character and creeps about in the follicles and genital canals of the female mussel. It 

 is able to penetrate the egg membrane (fig. 208) and sometimes even penetrates into the 

 very nucleus (fig. 211). Inside the egg it begins to grow in volume and the nucleus 

 divides into two, then four, etc., until a large number of nuclei are formed. The resulting 

 plasmodial mass forms a cyst (fig. 209), and the contained nuclei become simple, uninu- 

 cleate spores without undergoing any internal differentiation (figs. 210, 211). This 

 characteristic clearly places this protozoan in the genus Haplosporidium, which was 

 founded by Caullery and Mesnil (1899) under the name of Aplosporidium. Liihe 

 (1900), however, pointed out that the term was a misnomer, being evidently derived 

 from airXovs, meaning simple, and not from airXovs, which means unseaworthy, and 

 therefore should be Haplosporidium. 



Since this particular species parasitizes the egg of Mytilus, the author has given 

 to it the name Haplosporidium mytilovum. The parasites appear to be most abundant 

 late in the breeding season, and mussels which have retained their eggs until late in the 

 fall are most heavily infected. It may be, however, that infection by the parasite 

 prevents complete spawning, although the author has found quantities of the infected 

 eggs which were laid in the troughs where mussels were kept. Thousands of eggs in a 

 single individual may contain one or more cysts of the parasite. Whether its presence 

 does any more injury than to destroy the eggs has not been learned. It is the intention 

 of the writer to investigate the organism further and publish a more complete description 

 of its life history and habits. 



USES AND COMMERCIAL VALUE. 



Sea mussels are used in a variety of ways in different countries. In France they 

 constitute one of the principal marine food products, the value of the fishery being 

 approximately one-eighth that of the oyster fishery. The demand for mussels in France 

 exceeds what the nation is able to produce, although the most refined methods of myti- 

 culture are practiced in that country. Hundreds of thousands of bushels of the shell- 

 fish are imported annually from Holland and Belgium. They are also considered a 

 cheap and healthful food in Spain and Portugal. They are eaten to some extent in 

 Great Britain, Germany, and Norway, and are now beginning to be appreciated as a 

 wholesome food in this country. 



They rank next in importance as a bait in the fisheries, especially in Europe, where 

 they are considered the best hook bait known. The quantity used in Great Britain for 

 this purpose amounts to more than 100,000 tons annually. In America they are not 

 rated so highly as a bait, but are given preference when squid can not be obtained. 

 Mackerel fishermen often crush mussels and throw them overboard to attract the fish 

 to their boats. 



As a fertilizer they constitute another useful and important product. Where the 

 beds are exposed to the deposition of silt the mussels are gradually smothered to death, 

 while new generations are constantly becoming attached to the layers above. The result 

 after a number of years is a thick layer of blue, ill-smelling matter called mussel mud, 

 which is rich in lime, sulphur, and nitrogen. It is considered one of the best fertilizers 

 known, especially for carrots and onions. A writer from Essex County, Mass. (in Inger- 

 soll, 1884, p. 621), stated that for 30 years he had seen it applied to lands where onions 

 had been grown with a yield varying from 300 to 600 bushels per acre. The material 



