16 



GUIDE TO THE STUDY 



enter the pulmonary chamber of a preferred species of snail and 

 transform into sporocysts. 



By use of the appended key (p. 18) determine the genus of 

 the living snails furnished for this exercise. This done, carefully 

 snip away the shell and remove the snail to a dish of water. 

 Note the large respiratory chamber on the dorsal surface and the 

 very large yellowish or brownish liver which forms a large part of 

 the coiled portion of the snail. 



oral cap of spines. 



unp. aye spots 



/zenetration aland, 

 aenital pnmordtum \" ~^^£- 



duets -pen a lands 



ant. collecting tuba 

 -.body dir. CI. bladder 



post, collecting tube 



flame celts of tail 



caudal todies 



Fig. 5.- — Semi-diagramatic drawing of Cercaria longifurca. The body spina- 

 tion is shown only on the left side and the excretory system on the right. {After 

 Cort and Brooks.) 



At this stage there may be seen one or more clear colorless 

 worms about half an inch in length, with well-developed setse, or 

 bristles. These have no relation to the developmental stages of 

 the fluke but are commensal annelid worms of the genus 

 Chcetogaster. 



Open and examine the pulmonary chamber of your snail. In 

 a high percentage of specimens will be found the early larval 

 stages of some fluke. 



The sporocyst is an elongated sac with an outer cuticle, a thin 

 muscular layer, and an inner epithelial layer. In the interior are 



