42 MR. C. L. BOULENGER ON [Jan. 14, 



4. On the Hermaphroditism o£ the Amphipod^ OrcJiestia 

 deshayesii Audouin. By Charles L. Boulenger, B.A., 

 F.Z.S., King^s College, Cambridge. 



[Received January 11, 1908.] 



(Text-figm^e 14.) 



Otmar Nebeski (1), in 1880, was the first to call attention to 

 the interesting fact that in the male Orchestia cavimana Heller 

 (=0. gammarellus Boeck), the anterior portion of the testis 

 constantly gives rise to ova instead of spermatozoa. 



Delia Valle (2), in his Monograph of the Gammarini, partly 

 confirms this statement but remarks that, at least in the species 

 which he examined, 0. deshayesii Audouin, this phenomenon 

 was neither as common as Nebeski stated nor had he ever seen 

 so large a number of ova as figured by that author. He adds 

 that he has never observed ova in the testes of a fully adult male, 

 but only in a few individuals which, although of large size, yet 

 retained juvenile characteristics in the shape of the posterior 

 gnathopoda. 



Geoffrey Smith (3), struck by the discrepancy of the above 

 results, examined specimens of Orchestia at Naples during 

 December to March 1905-6. On dissection he found that more 

 than 50 per cent, of the males belonging to both species, whether 

 fully developed or not, exhibited ova in their testes. He there- 

 fore came to the conclusion that Delia Yalle could not have 

 examined 0. deshayesii during the winter months, and that in 

 the summer, when these animals breed, the fully-developed males 

 lose these ova. As he remarked : — " The males of these species 

 when breeding is not going on assume a semi-hermaphrodite 

 condition of a quite indubitable kind which must evidently bear 

 some relation to the metabolic conditions in the body." 



The particular metabolic condition which calls forth the pro- 

 duction of these ova is, he thinks, that condition of " adaptive 

 anabolism " which he has studied in the infected males of various 

 animals subjected to " parasitic castration " and in the middle 

 males or males of suppressed sexuality in " high and low 

 dimorphism." 



During a recent stay at Naples I undertook this investigation, 

 at the suggestion of Mr. Geofl'rey Smith, with the object of ascer- 

 taining what evidence could be obtained in support of his results. 



The two commonest sandhoppers at Naples are Orchestia 

 deshayesii and Orchestia, gammarellus ; although a certain 

 number of individuals belonging to the latter species were 

 examined, most of my observations were made on 0. deshayesii 

 as being the more suitable form for an investigation of this kind. 

 The chief reasons for this choice were : — 



(1) 0. deshayesii could be obtained in large numbers close to 



