Chapter 5. 



The effect of the Parasites on their Hosts. 



(With Plate 7 figs. 1—21.) 



Contents. 



1. The general effect of Sacculina neglecta on Inachus scorpio. 



2. The effect on the primary and secondary sexual characters of I. scorpio. 



A. Effect on the secondary sexual characters. 



1. Males. 



2. Females. 



B. Effect on the primary sexual character. 



C. Crabs of apparently doubtful sex. 



D. The sexual condition of recovered crabs. 



1 . In a state of Nature. 



2. Crabs experimentally freed from Sacculina in Aquaria. 



3. The cellular origin of the regenerated gonad. 



3. The Case of Eriphia spimfrons. 



A. The simultaneous parasitism of Entoniscidae and Rhizocephala. 



B. The nature of the parasitic castration in Eriphia spimfrons. 



4. The Case of Pachygrapsus marmoratus. 



5. General Conclusions and Summaries. 



6. Special Reference of the phenomena of Parasitic Castration to High and Low 

 Dimorphism. 



Zool. Station zu Neapel, Fauna und Flora, Golf Ton Neapel. Rhizocephala. 



