HISTORY OF CRUSTACEA. 



CHAP. V. 



on the feet of the third and fourth pairs (fig. 12) has 

 long been known, although its connexion with the 



branchial cavity has 

 not been suspected. 

 These two pairs of 

 feet are more closely 

 approximated than 

 the rest; the op- 

 posed surfaces of 

 their basal joints 

 (therefore the hind- 

 er surface on the 

 third, and the an- 

 terior surface on the 

 fourth feet) are 

 smooth and po- 

 lished, and their margins bear a dense border of long, 

 silky, and peculiarly formed hairs (fig. 13). Milne- 

 Edwards who rightly compares these surfaces, as to 

 their appearance, with articular surfaces, thinks that they 

 serve to diminish the friction between the two feet. In 

 considering this interpretation, the question could not 



and die, not because they are under water but because they have con- 

 sumed all the oxygen which it contained. I therefore put into the 

 same water from which I had just taken an unconscious Ocypoda, with 

 its legs hanging loosely down, a specimen of Lupea diacantha which 

 had been reduced to the same state by being kept in the air, and this 

 recovered in the water just as the Ocypoda did in the air. 



2 Fig. 12. Posterior entrance to the branchial cavity of Ocypoda 

 rhorribea, Fab., nat. size. The carapace and the fourth foot of the right 

 side are removed. 



3 Fig. 13. Points of gome of the hairs of the basal joints of the foot, 

 magn. 45 diam. 



Fig. 13. 3 



Fig. 12. * 



