FRESH- WATER MUSSELS. 137 



habits and the development of mussels, while Simpson (1899, 1900, 1914, etc.), Walker 

 (1913, 1918, etc.), Ortmann (1911, 1912, 1913, etc.), and others have greatly extended 

 our information regarding classification, distribution, and structure. 



With the establishment of the Fisheries Biological Station at Fairport, Iowa, and 

 the begirming of its scientific work in 1908, the studies pursued by the scientific staff 

 of that station, in connection with the propagation of mussels, made still further advances. 

 Chief among the results of the studies conducted at this station may be mentioned the 

 discovery that particular species of mussels are restricted in parasitism to one or a few 

 species of fish, the rearing of young mussels in quantity from artificial infections upon 

 fish, the demonstration that the glochidia of certain species of mussels may grow mate- 

 rially in size during the period of life on the fish (being, therefore, true parasites) , and the 

 observation that one noncommercial species of fresh-water mussel nonnally completes 

 its life history without a stage of parasitic life." 



Finally it should be remarked that one of the most difficult of all gaps to bridge 

 was the rearing of j'oung mussels after they leave the fish. Strange as it may seem, 

 all attempts to keep alive and to rear the young mussels under conditions of control 

 failed of result. Lefevre and Curtis (191 2, pp. 182, 183) recorded the rearing from an 

 artificial infection of a single young mussel which attained a size of 41 by 30 mm. In 

 1 91 4, however, Howard was successful in rearing over 200 Lake Pepin muckets from 

 an artificial infection, when the infected fish were retained in a small floating basket in 

 the Mississippi River (Howard, 1915). These mussels attained a maximum size of 3.2 

 cm. in the first season; and in subsequent years many of them were reared to maturity, 

 the glochidia developed from their eggs were infected upon fish, and a second generation 

 was reared to an advanced stage. In that year (1914), too, Shira, using watch glasses 

 and balanced aquaria, reared a few mussels from an artificial infection to a maximum 

 size of 0.44 cm. in 291 days. In the same year, though from an experiment initiated 

 by the senior author in the fall of 1913, young mussels were reared in a pond, from an 

 artificial infection of fish liberated in the pond, to a maximum size in the first season of 

 3.5 cm. Some of these mussels at the age of 4 years had attained sizes suitable for 

 commercial use in the manufacture of buttons. The same species, Lampsilis luteola 

 (Lamarck), known as the Lake Pepin mucket, was used in all of these experiments. 

 Subsequent experiments on a larger scale conducted both at Fairport and in Lake 

 Pepin are mentioned on a later page. 



AGE AT WHICH BREEDING BEGINS. 



The age at which mussels begin to breed varies with the species. There is reason 

 to belie^•e that the paper-shell, Lampsilis (Proptera) Icevissima, breeds in the same sum- 

 mer during which it leaves its host or when just i year of age from the egg. Anodonta 

 imvecUiis and Plagiola donacijonnis apparently breed in the second summer. The small- 

 est breeding Ouadrula observed was a pig-tue, Quadrula uiidata, 30 mm. (about 1.2 

 inches) in length, and 4 or 5 years of age as evidenced by the interruption rings. The 

 smallest washboard, QuadrtUa heros, observed ia breeding condition was 91 mm. (3.58 



" Lefevre and Curtis (1911) had previously observed and reported the fully developed juvenile mussels iu the z^WsxA Strophttus 

 edeniulus. Later. Howard (1914) while showing that the glochidia of that species will become parasitic on fish and undergo devel- 

 opment imder the usual conditions, discovered that another species, Ancdoyifa imbecilhs. normally develops without the aid of 

 fish. (See p. 156, below.) 



