Hapalocardnus, the Gall-forming Crab, etc. 



59 



The male is figured in the ventral and dorsaal spects where, though 

 it is so small, it will be seen that none of its organs show any signs of 

 degeneracy. This is so for the internal as well as the external organs. 

 The alimentary canal is apparently quite normal; the buccal append- 

 ages resemble almost exactly those of the female. Yet it will be seen 

 that the reproductive organs reach a remarkable state of development. 

 The opaque white structures which I have referred to above occupy 

 a large part of the dorsal surface of the cephalothorax. The fact that 

 they are full of mature spermatozoa leads one to regard them as 

 vesicul* seminales rather than testes and it is difficult to recognise in 

 them the tubular shape of the testes and vasa def erentia of the Deca- 

 poda generally. A noticeable point is that the spermatozoa all lie 

 free in vesicula seminalis and are not contained in spermatophores. 

 The absence of tubular testes at the time of examination is probably 

 due to the fact that the male is short-lived and spermatogenesis is 

 confined to a short period, during which all the germ cells are rapidly 

 used up and enormous numbers of spermatozoa are produced. 



FIG. 13. Copulatory appendages of male of Hapalocardnus. X 50. app. 1, first abdominal 



appendage; app. 2, second abdominal appendage. 

 FIG. 14. Third maxillipwl of male Hapalocardnus. X 80, to show the small number of setae 



fringing the inner border. 



The spermatozoa are very tiny discs about 5 ju in diameter. They are 

 without marginal processes. 



In the female, spermatozoa are found in the spermathecse, which 

 are rather large, rounded sacs in the ventral part of the body cavity, 

 just at the female openings. They are exactly like those seen in the 

 vesicular seminales, but are cemented together evidently by a substance 

 secreted by the spermathecal epithelium. 



As is usual in the Brachyura, the appendages on each side of the first 

 two abdominal segments unite to form a single copulatory organ. 

 The anterior appendage is tubular; its cavity is large at the base, but 

 soon diminishes greatly and only widens again at the tip where it opens. 



