8 ILLINOIS BIOLOGICAL MONOGRAPHS [226 



METHODS OF INVESTIGATION 



The methods employed in this study are those ordinarily used with 

 similar material. No special technique has been found necessary. In 

 general sections were stained in toto with Erlich's acid hematoxylin and 

 counterstained in section with alcoholic eosin. Sections were cut 10 to 

 20 micra in thickness. Frontal, sagittal, and transverse sections were 

 used. In order to obtain a clearer perception of more minute and obscured 

 parts wax reconstructions were made. These were employed particularly 

 to find the relationship and constancy of form of the female genital organs. 



MATERIAL 



The material on which this study is based is composed of various collec- 

 tions from different regions of the United States. It is limited to that 

 obtained from North American fresh water hosts and in each instance is 

 listed with the species description. However for comparison with the 

 Amerian material the following specimens were secured from the sources 

 indicated. 



EUROPEAN MATERIAL 

 From the Zoological Museum, Berlin 

 Species 

 Cyclocoelum problemalicum 

 Cyclocoelum problemaiicum 

 Cyclocoelum problemalicum 

 Cyclocoelum ovopunclatum 

 Cyclocoelum brazilianum 

 Cyclocoelum tringae 

 Haematotrephus similis 

 Haematotrephus similis 

 Monostomum vanelli 



From the Zoological Museum, University of Gottingen 

 Cyclocoelum (Monostomum) Gallinula chloropus 284 Mehlis 



mutabile (Zed.) Taken at Claustal 



Monostomum verrucosum Anas bernicla 234 Mehlis 



Monostomum attenuatum Mergus merganser 238 Mehlis 



Monostomum attenuatum Anas juligula 220 Mehlis 



From the Zoological Museum, University of Vienna 

 Monostomum mutabile Totanus flaviceps IX 552 



Taken in Brazil 

 From the Collection of Henry B. Ward, University of Illinois 

 Collyriclum faba Passer domesticus 21.764 Zschokke 



Taken in Switzerland 



NORTH AMERICAN MATERIAL 

 From the Leidy Collection 

 Cyclocoelum leidyi Gallinago uilsoni 160 Leidy 



(Monostomum mutabile 

 Zeder of Leidy) 



