1908.] HERMAPHRODITISM IN AN AMPHIPOD. 45 



the possession of an enlarged nucleus which hardly stained with 

 carmine oi" hfematoxylin. 



Owing to the difficulties of dissection only a few individuals of 

 this age wei-e examined, but all (8) possessed ova of various sizes. 



In older specimens, varying in size from 10-13 mm., these ova 

 were found to be of greater size and to occur in greater abundance. 

 Their exact position in the testis varied slightly, but usually the 

 anterior third only was ovigerous. 



The ova at this stage have evidently grown at the expense of 

 the surrounding germ-cells, which have disappeared, and come to 

 lie loose in a cavity surrounded merely by the external epithelium 

 of the testis. A kind of egg-sac is thus formed separated by a 

 constriction from the postei-ior part of the male gland where 

 sperm-production is proceeding with great activity. 



In a few specimens, in addition to the ova at the anterior end, 

 others were to be found among the developing spermatocjiies in 

 the posterior part of the testis. 



The greatest number of ova ohsei'ved in any testis was 1 2 ; this 

 number falls considerably short of that recorded by Nebeski ; that 

 author figured as many as 29 in a testis of Orchestia gammarellus. 

 Altogether 198 males were examined at this stage, and of these 

 only 19 were devoid of ova. 



The fate of these ova I have not been able definitively to ascer- 

 tain, they have never been seen in the vesicul^e seminales or in 

 the vasa deferentia, and from their position it is highly improbable 

 that they ever reach the exterior. In several testes examined by 

 me the ova w^ere much shrivelled, and it seemed as if they were 

 being resorbed by the rest of the testis. 



As the result of this investigation, it seems that ova are of 

 normal occurrence in the generative organs of the young males ; 

 later, when these animals attain maturity and acquire their adulfc 

 characters, these ova in most cases disappear and are probably 

 absorbed by the rest of the organ before the final moult. 



These results are therefore much at variance with those obtained 

 by Smith, and I am at a loss to explain how he arrived at his con- 

 clusions ; I can only suggest that they may be due to his not 

 having sufficiently separated the adult and the young males during 

 the course of his observations. 



That ova should be developed chiefly in the testes of immature 

 males of Orchestia need cause no surprise, for similar j)henomena 

 have been described in numerous animals. This type of " histolo- 

 gical " hermaphroditism seems particularly common in Vertebrates, 

 this being probably due to the fact that this group has been more 

 exhaustively studied than any other. A number of cases have, 

 however, been recorded among the Invertebrates : — Ova have been 

 described by Krohn (5) as normally occurring in the testes of 

 Phcdangium ; Gai-nier (6) has found them in Astacus, Ischikawa(7) 

 in Gehia, and recently so have Smith (3) and Potts (8) in other 

 Crustacea {Inaclms and EujKigurus) as the result of " parasitic 

 castration." 



