UNIVERSITY OF CALIFORNIA PUBLICATI 



ZOOLOGY I 



Vol. 19, No. 11, pp. 335-388, plates 19-25, 1 figure" i"n text May 15, 1920 



THE LIFE CYCLE OF ECHINOSTOMA 

 REVOLUTUM (FROELICH) 



BY 



JOHN C. JOHNSON 



CONTENTS 



PAGE 



Introduction 335 



Methods of study 336 



Acknowledgments _ _ 337 



Eggs and development of miracidia 338 



Infection of snails and development of mother-rediae 341 



Rediae containing daughter-rediae 342 



Rediae containing cercariae 344 



Cereariae -..- 346 



Excretory system of eercaria 348 



Encysted agamodistomes or cysts _ 361 



Adults 365 



Theoretical discussion of the life cycle 368 



Literature cited 373 



Explanation of plates 376 



INTRODUCTION 



Although many different species of adult echinostomes have been 

 recorded, nowhere in the literature do we find the description of all 

 the stages of their life cycle. In 1909, Liihe (1909, p. 65) clearly 

 stated that up to that time the life cycle was insufficiently known and 

 that no eercaria had been identified as belonging to a definite adult 

 echinostome. The nearest approach to finding all the stages of the life 

 cycle was made by Nicoll (1906, 1906a) and Lebour (1908) in their 

 work on Echinostomum secundum Nicoll. However, these workers 

 definitely state that no stages before the redia with cercariae inside 

 were seen. Since that time neither in Europe nor America have all 



