SOUTHERN OYSTER DRILL AS A PREDATOR 



83 



invasion site itself. At 24 and 72 houi-s after drills 

 were first exposed to numerous niiracidia, very 

 young first generation rediiie were found in the 

 tissues of the head and columellar muscle as well 

 as in the arteries, veins, sinuses and tissues of the 

 siphon, foot, eyestalk, mantle, kidney, and visceral 

 mass (figs. 2, 3, 5.) 





Figure 2. — Very young redia in large vein next to colu- 

 mellar muscle ; 24-hour experimental infection ; G, 

 DH-AzB-E; X210. 



.-^i 





FiouBE 3. — Very young redia, parts of two others, in 

 large vein near digestive gland, 72-hour experimental 

 infection; PFA-3, DH-AzB-E ; X210. 



'"Ssai^ 



-j^ 



Figure 4. — Much older redia in renal blood sinus ; nat- 

 ural infection ; Z, DH-AzB-E ; X215. 





Figure 5. — Very young redia entering sinus in siphon 

 wall ; 72-hour experimental infection ; PFA-3, DH- 

 AzB-E ; X210. 



By the eighth day, the rediae had grown 

 markedlj' and germ balls (embryos of the next 

 larval generation) had begun to appear inter- 

 nally, (fig. 4), but the rediae were still found in 

 much the same Igcations as during the first three 

 days of infection. 



