86 L. A. BORRADAILE. 



It may be that the stimulus of lifting the branchiostegite is sufficient to set the appendage 

 in motion, but in this case one would expect the movements either to cease directly or to 

 continue as long as the branchiostegite is raised. This is not what happens, the movements 

 being sometimes steady and sometimes fitful and irregular. A third explanation, and the 

 one which at present seems the most probable, is that we have here an instance of a 

 vestigial habit, retained after it has ceased to be of use to the animal. Lastly, if it could 

 be shown that both sexes are in the habit of going into the water at frequent intervals, 

 yet another solution of the question could be offered. For in that case it would be jwssible 

 to suppose that the motion of the scaphognathite was retained on account of its being 

 indispensable to the animal under water and at the same time, for some physiological 

 reason, not susceptible to inhibition for long periods and thus perforce continued on land. 

 But this view would require assumptions, which there is no justification for making. 



Abdominal respiration. At the time of my sojourn in the Island of Minikoi, I was 

 unaware of Bouvier's' researches on this point. My own observations were much less com- 

 plete than his, but I can confirm his statements with regard to the various channels 

 carrying blood back from the abdominal walls to the pericardium, at least as regards the 

 dorsal pair, the ventral I failed to observe. While he paid considerable attention to the 

 anatomical side of the question, Bouvier does not appear to have made any experiments 

 to test his theories. It is interesting to observe that if the gills of both sides be cut off, 

 leaving small stumps to avoid loss of blood (it would be better to ligature the gills in a 

 future experiment), the animal is still capable of living. Indeed one, on which I performed 

 this experiment, lived several days, and finally escaped from the vessel it was confined in. 

 Taken in conjunction with the fact that the action of the scaphognathite may be suspended 

 without harm to the animal, this fact seems to indicate that abdominal respiration is of 

 considerable importance in Coenobita. It is further interesting to note that the soft skin 

 of the abdomen is always damp. Possibly the object of the hairs and fleshy processes on 

 the ventral surface of the abdomen is as much to retain water as to play any part in 

 respiration by movement, as Bouvier suggests. It would certainly appear, from the elaborate 

 precautions taken in various groups of land Decapoda to ensure the presence of moisture 

 on the breathing organs, as though respiration were, in them at least, impossible except 

 through a moist surface. 



V. Kidneys (green glands) (PI. III. fig. H). 



The kidney of Coenobita is a large oval cushion, of a pale greenish colour in the living 

 animal, placed in the head on each side of, and rather behind, the brain, and behind the 

 base of the antennae. The surface of the cushion is not even, but raised into a number 

 of irregular rounded lobes, except in the middle of the upper side, where a space is left 

 smooth, and forms a depression amongst the lobes. The hilum of the gland is in front 

 and on the outside. I am quite unable to distinguish, by injection or otherwise, any vesicle 

 such as is found in nearly all other Decapods and is especially well developed in the 

 Pagurids. The only other instances in which this does not occur are quoted by Marchal 



' Bouvier, Bull. Soc. Philomath., Paris (8), ii. p. 194 with the pericardium on each side by two veins — a long 

 (1890). Briefly put the apparatus consists of a tegumentary dorsal and a short ventral one. The two veins of each side 

 plexus, fed from the abdominal sinus and communicating join before entering the pericardium. 



