632 RKCORD OF CURRENT RESEARCHES RELATING TO 



slender, carry small diclfe, and arc rendered more mobile by the fact 

 that the fore-arm is broken up into a number of small joints : the 

 first pair of legs is strong, with powerful cheloB. In the hermit-crabs, 

 the porccllanoiis crabs, and the Galatheidso, on the other hand, it is 

 the fifth jiair which is thus used ; they are thin, with very mobile 

 joints, have small pincers well supplied with brushes, combs, &c. ; 

 they chiefly act on the gill-pouch. A commensal Porcellana living 

 with an especially mucous worm, was observed to keep these limbs in 

 constant motion over all parts of the body. In the crayfish, lobster, 

 and prawn none of the pairs of feet appear adapted for this purpose. 



In the Crabs, each of the six maxillipedes bears a long process, 

 pointing backwards, the edges thickly set with long hairs ; the 

 whole has the outline of a sabre, and acts like a dusting-brush. The 

 one belonging to the first pair lies outside the branchial cavity, the 

 other within it, where they constantly play backwards and forwards 

 between the branchiae and the carapace. The hairs which clothe them 

 show an immense variety in the form and arrangement of their teeth, 

 of which Trichodactylus, Gelasimus, Hepatas, and Lupea afford in- 

 teresting examples. In Trichodactylus the inner wall of the chamber, 

 too, bears a number of small protuberances, each terminated by a 

 spine ; the function of the spines is to cleanse the hairs of the brushes 

 above mentioned, as they pass to and fro. Trichodactylus is also 

 remarkable, though not entirely peculiar, for leaving the egg as a 

 fully developed crab. 



Anal Respiration of the Copepoda.* — Mr. M. M. Hartog, in a note 

 on Cyclops read at the British Association,t pointed out that its respi- 

 ration was exclusively anal. He has now made out the same in 

 Canthocamptus (fam. Harpacticidas), and Diaptomus (fam. Calanidje). 

 In all three the mechanism is the same ; at regular intervals, after 

 the backward sway of the intestine, the anal valves open for an 

 instant and then close, giving just time for a slight indraught of 

 water after the opening, a slight expulsion at the close. The necessary 

 pressure to confine the animal seems to interfere somewhat with these 

 movements, sometimes stopping them, if excessive ; hence he " refrains 

 from noting with illusory exactness the intervals between each 

 respiratory movement." 



It is to be noticed that the rectum contains as a rule liquid only, 

 the bolus of faeces remaining in it but a short time. By endosmose 

 the liquid in the rectum will tend to be at the same condition of 

 gaseous saturation as the body-fluid around it, kept constantly agitated 

 by the backwards and forwards sway of the stomach. During the 

 short interval that the anus is open an approach to gaseous equilibrium 

 with the external water takes place, even despite the very slight move- 

 ment of the water (shown by the little change of place undergone by 

 suspended indigo or carmine particles). In the absence of any other 

 suitable respiratory apparatus, no one can hesitate as to the function of 

 the action described. 



In the Nauplius larvae of Cyclops and Diaptomus the working is 



* ' Quart. Jonin. TMicr. Sci.,' xx. (1880) p. 244. t ^ntc, p. 254. 



