Figs. 1 and 2. An adult and gravid female (La7npsilis luteola Lam.) grown 

 in nature. The right shell and mantle were removed to expose the soft 

 parts of the mussel. At M may be seen the marsupium a modified por- 

 tion of the outer gill in which the young are carried from the egg to the 

 glochidial stage. Photograph natural 9ize; by the author. 



Figs. 3, 4 and 5. Mussels of the same species as in Fig. 1. reared under con- 

 trol in a crate, from glochidia metamorphosed on artificially infected fish. 

 The mussels are in their first, second and third years, respectively. 

 Photograph natural size; by J. B. Southall and the author. Fig. 3. is a 

 gravid female at the age of first breeding two years and sixty-seven days 

 after metamorphosis. 



