299] NORTH AMERICAN MONOSTOMES 81 



SUMMARY 



I. Monostomes from North American land and fresh water hosts have 



been studied. 

 II. Nine new species have been described in detail. 



III. The knowledge of their anatomy and life history is greatly increased. 



1. Both oral sucker and pharynx are present in the Cyclocoelidae. 



2. In the genera of Cyclocoelidae studied the receptaculum seminis 



is a constant feature while Laurer's canal is not present. 



3. The origin of the ventral glands in Notocotylus urbanensis is 



clearly shown in early stages of development. 



IV. The discovery of well developed miracidia in Collyriclum colei renders 



improbable Jegen's account of the life history of Collyriclum faba. 

 V. A careful study of the anatomy of the Cyclocoelidae, the Notocotyli- 

 dae, the Collyriclidae, and the Heronimidae demonstrates clearly 

 that they are not immediately related. 



1. The Cyclocoelidae are probably allied to the Fasciolidae. 



2. The Notocotylidae are closely related to the Pronocephalidae 



not merely in general organology but especially in the presence 

 of peculiar ventral glands. 



3. A study of the organology of the Collyriclidae demonstrates 



clearly their direct relationship to the Pleurogenetinae. 



4. The Heronimidae do not show immediate relationship to any 



known trematodes. 



VI. The monostomes are a heterogeneous group and must ultimately be 

 distributed among other groups in accordance with their funda- 

 mental relationships. 



