78 



The effect of the Parasites on their Hosts. 



Thus there were 16 infected males and 31 infected females which showed no modi- 

 fication at all, while out of 47 hermaphrodite forms only 16 were infected with Sacculina. 

 This constituted in Dr. Duncker's opinion a strong objection to the view that the herma- 

 phrodite form had anything to do with the presence of the Sacculina. Dr. Duncker very 

 kindly put about twenty of the specimens of hermaphrodite form at my disposal, and on 



Text fig. 21. 



dissecting them I found that everyone without exception contained a specimen 

 of Entoniscus. The gonads in these specimens appeared to have totally aborted. 



The fact that Entoniscus may effect the parasitic castration of its host has been known 

 for a long time owing to the researches of Giard & Bonnier, and it appears that in this 

 case, whereas the Sacculina has little or no power to bring about the castration, this is 

 effected completelj by the Entoniscus. 



