504 



FRESH-WATER BIOLOGY 



Fig. 8io. Mesomermis virginiana. 



a, mouth opening; b, lateral organ; c, esophagus; d, nerve-riog; e, posterior end esophagus; /, i: 

 , blind end anterior testicle; h, testicle; t, junction of testicles; j, intestine; k, blind end | 



, intestine; 



^, . . ... . ,, , . posterior 



testicle; I, ventral supplementary organs; m, submedian supplementary organs; n, oblique copulatory 

 muscles; o, spiculum. (.After Cobb.} 



