2 UNIVERSITY OF MISSOURI BULLETIN 



The investigators who first studied the glochidium during 

 its parasitic life refer only incidentally to the relation of the 

 larva to its host. 



Leydig (11) in 1866 made the discovery that the glochi- 

 dium lives for a time as a parasite on a fish. 



Forel (6) in the following year succeeded in finding fishes 

 wkh,glochidia : embedded on different parts of the body. He 

 observed that fh'e c^et in which the glochid um lives during the 

 -parasitic; period is Compjosed of epithelial cells and that after 

 ' the *la"rva *atta*cii'e5 its"elf to the fish the cells of the epitheluim 

 around it begin to multiply and gradually enclose it. Forel 

 estimated that the glochidium remains on the fish from three 

 to four months. 



Braun (1, 2) was the first to make an artificial infection 

 by removing glochidia from the gills of the mussel and putting 

 them with fishes in a vessel. He was able in this way to obtain 

 material for studying the glochidium during the entire post- 

 embryonic development. He found that the larval mantle 

 cells grow out into the mantle cavity and form fungus-like 

 bodies. Later investigators agree with him in believing that 

 the function of these larval mantle cells is to take up, as food, 

 the fish's tissues enclosed between the valves of the shell. In 

 describing the formation of the cyst he says that by the irrita- 

 tion of a foreign body the cells of the fish's epidermis are caused 

 to grow and rise up around the larva, completely surrounding 

 it in three or four days. Braun also discovered that the tem- 

 perature of the water affected the duration of the parasitic 

 period. 



Schierholz (14) made a number of infections in order to 

 determine the length of time that the glochidium remains on 

 the fish and found that it varied from fourteen days in July 

 to five months during the winter. He states that the time re- 

 quired for the formation of the cyst varies with the size of the 

 blood vessels which are ruptured by the larva when attachment 

 occurs; the larger the vessels the more rapidly is the cyst com- 

 pleted. In some cases the glochidium is covered in two or three 



