504 PROF. J. E. DUERDEN ON CRABS [ Dec. 12, 
to stimuli take place in a Melia deprived of its actinians as when 
they are present, but the empty chelipeds make no attempt what- 
ever to grasp the source of irritation as in ordinary crabs. The 
movable joint (dactylopodite) remains partly open, to about the 
same degree aS when holding an actinian, and its use as an 
organ for direct protection or attack seems to have altogether 
disappeared. 
The responses of the chelipeds are manifestly so many instinctive 
reflexes on the part of the crab, directed towards the region whence 
the irritation comes, and are carried out independently of the 
presence or absence of the actinians. When the latter are in 
position, the reactions may be assumed to be aggressive or pro- 
tective in their nature; while when taking place in the absence 
of the polyps they are of no protective value, as the claws are 
useless for grasping or seizing. 
Compared with most crabs, it would seem that there is in Melia 
a marked increase in the power of directive response on the part 
of the chelipeds, accompanied by a loss of activity on the part of 
the movable joint which ordinarily serves for aggressive purposes ; 
moreover, the chelipeds as a whole are greatly reduced in size, 
Frepine REACTIONS. 
Under ordinary circumstances, the Melias were often seen trans- 
ferring towards their mouth the débris occurring on the bottom 
of vessels or other objects over which they passed. This they 
accomplished by means of the maxillipeds, with the assistance of 
the first, second, and even third pair of ambulatory limbs, the 
first ambulatory pair being the most active. The débris was 
seized by the maxillipeds, and the nutritive particles were ingested, 
and the non-nutritive rejected and wafted away posteriorly. The 
chelipeds, whether empty or holding actinians, took no part 
whatever in the feeding processes. Even fragments of meat given 
directly to the crab were treated in the same manner ; their 
passage to the masticatory appendages was effected by the first 
ambulatory limbs, always without the assistance of the chelipeds. 
As the actinians were dragged about from place to place, débris 
readily adhered to them by means of the viscid slime with which 
they were covered, and very frequently the first ambulatory limbs 
were applied to the polypal walls, and the latter were thoroughly 
cleansed from any adhering particles. The operation was carried 
out much in the same way as that by which the crab cleansed its 
own limbs. During the process the actinians were brought close 
to the mouth, and the débris removed was easily transferred 
thereto by the appendages. Some of the particles were nutritive, 
and there is no question that the crab will frequently secure food 
material thus mechanically adhering to the walls of the polyp. 
No instance was observed where the crab applied its appendages 
to the general body-surface of the polyps except when foreign 
particles were adherent. Durimg the cleansing treatment the 
