608 F. A. POTTS. 



By dissection of these crabs of problematical sex it was in 

 rare cases possible to discover a diminished gonad, and on 

 such occasions this was more often an ovary than a testis, 

 though instances of both were found. The appendages of 

 these animals vary from slightly modified to completely 

 female type, but the former part of the series is represented 

 by only a small number of individuals. Probably then the 

 slightly modified individuals and a small percentage of the 

 fully modified belong to the male sex, while the rest which 

 form a majority are really females. 



In Carcinus moenas infected by Sacculina, as described 

 by Giard, the old males are entirely unmodified, and the 

 varying amounts of modification in different individuals are 

 hence connected with the age at which they became infected. 

 Though the solution of the question is to a certain extent 

 interfered with in Eupagurus meticulosus by the con- 

 tinued growth after the external appearance of the parasite, 

 yet the observation that young males of I'O — 1'3 cms. cara- 

 pace length were perhaps more often than not unmodified, 

 while the largest infected males found of 1*6 — 2*0 cms. cara- 

 pace length were equally likely to be modified or unmodified 

 shows that in this case the male sexual characters are not 

 more susceptible to alteration of type at an earlier age. It 

 has also been pointed out above that the degree of modifica- 

 tion is independent of the presence of a larger or smaller 

 parasite, of one or a greater number. 



Apparent modification in the female. 



Although the majority of the infected females resemble 

 the young rather than the adult normal female with regard 

 to the development of the internal ramus, yet cases in which 

 any real approach to the uniramous condition is found are 

 extremely rare, and I have been only able to procure three 

 specimens which were, in Giard's sense, clearly modified 

 toward the male type. All three were of small size; in no 

 case were any of the first three appendages of pure male 



