4. 



of the mter must as withdrawn to alow down the movement 

 of the animal* When a slight aiaount more of ^ater IB 

 withdrawn, due to evaporation, the body wall quio>ly 



breads in many places. Jor this reason gre^t numbers 



' 



of ceroari'ie axd to bo studied before the system was 

 worked cut. 



? . <. t ru t 

 I wish here to ^press my thao^s to Mr. 



Walfr-ar of Detroit, Michigan and Mrs. Oldtoyd of Stanford 



CA 



University for identification of snail host*; to Mr, 



* "' 



John Maclaron, Superintendent of Golden Gate Par>, for 

 permission to obtain wat*r~fowl in said parh; to Mr* 

 Charooutte of Golden Gate ParV and those under his 

 oharge and to Hr* C. Cr* Budd, ep^oial garai<5 warden and 

 polioeiaan of 3an Pranoisoo, for oollectinu and shipping 

 the swans, mud hena and duc^a ; to Mr* J 1 * II* .'iiallou.of 

 the Department of Zoology, for collecting snails and other 

 materials used in this study; to Br* Joseph Grinnell and 

 iir. i'raoy X Storer,of the Museum of Vertebrate Zoology, 

 for identification of vertebrate hosts; and to Kr** Johnson 

 for directing the experimental feeding of ctiioks and 

 duelings and for help in various T ays. 



*Q Professor W, W, Port, under whose direction this 

 study haa been made, I wish hc?re to express say appreciation 

 for hie continued interest an<i many helpful suggestions. 



