Article III. — Studies on the Bnchytrcddcc of North America* 

 By Paul S. Welch, Ph.D. 



Introduction 



In spite of the fact that the forms belonging to the family Bn- 

 chytrccidcc are common in many parts of North America, it is a group 

 of which little is known. Less than a dozen references constitute the 

 literature on the North American species. The writer has been carry- 

 ing on investigations in this field in Illinois for the last three years, 

 and the following paper represents some of the results of this study. 

 He wishes to express his indebtedness to Professor Frank Smith, un- 

 der whose direction this work has been done. Acknowledgments are 

 also due as follows : to the Director of the Sewage Testing Station 

 at Chicago, for permission to work in the laboratories of that institu- 

 tion; to Dr. Arthur Lederer, chief chemist of the Testing Station, and 

 to his associates, for the many courtesies extended to the writer dur- 

 ing his work at that place; and to Professor S. A. Forbes, for ma- 

 terial from the collections of the Illinois State Laboratory of Natural 

 History. 



The Bnchytrccidcc, as known at present, include sixteen genera 

 and a large number of species. The family is wide-spread in its dis- 

 tribution, being common in various parts of the American continent, 

 generally distriljuted in Europe, and reported from Siberia, New Zea- 

 land, and North Africa. It appears, however, to be largely confined 

 to the cold and temperate regions of the world. Specimens of the 

 family have been met with upon the ice of the glaciers ; and twenty- 

 seven species have been recorded for Alaska. The warm sections of 

 the globe apparently have a very limited enchytrreid fauna, since only 

 a small number of species have been reported from them. Enchytrzeids 

 are found in various kinds of situations. Many are terrestrial, some 

 are aquatic, and others are reported as being amphibious. Although 

 the majority of the aquatic forms are fresh water species, several 

 species are found in marine situations. Bnchytrceidce are c|uite similar 

 to the earthworms in some respects, having (i) the simple setse, (2) 

 the wide separation of the spermathecre from the spermiducal pores, 

 (3) paired or unpaired glands comparable to the calciferous glands 

 of earthworms, and (4) the thick body wall. In other respects they 



*Contributions from the Zoological Laboratory of the ITniversity of Illi- 

 nois, under the direction of Henry B. Ward, No. 26. 



