CONTENTS 



PAGE 



Introduction 123 



Key to the genera of North American Eiicliytraridcc 125 



Henlea Michaelsen 126 



Key to species of Hciilca known to occur in North America 127 



Henlea inodcrata n.sp 128 



Henlea urbancnsis n.sp 134 



Lumbricillus Oersted 141 



Key to species of Lximbricillus known to occur in Nortli America 142 



Lumbricillus rutilus n.sp 143 



Fridericia Michaelsen 151 



Key to species known to occur in North America 152 



Fridericia douglasensis n.sp 154 



Fridericia oconeensis n.sp 159 



Fridericia sima n.sp 163 



Enchytrceus Henle 167 



Key to species known to occur in North America 169 



Enchytrceus gillettcnsis n.sp 170 



1 he penial bulb as a character in classification 173 



Observations and experiments on Lumbricillus rutilus n.sp 180 



Habitat 180 



Color of living specimens 184 



Locomotion 185 



Relation to light 186 



Relation to desiccation 186 



Thigmotactic response 187 



Behavior with reference to dry and moist surfaces 188 



Relation to temperature 188 



Relation to oxygen 189 



Relation to sewage 193 



Summary 202 



Bibliography 205 



Explanation of plates 211 



