MOUTH-PARTS OF THE SHORE CRAB. 137 
to follow because they are bidden by the third inaxillipeds. After the 
removal of the latter, movements of the inner jaws may be observed, but I 
.have not been able to induce crab.« which have been so operated upon to 
feed *, and in any case their feeding would not be normal. The second 
maxiliipeds apply to the, food their last joints, armed with the strong spines 
which have been mentioned. With these they s-oinetimes thrust outwards, 
aiding the third maxiliipeds or, if the morsel be small, even taking their 
place. At other times they appear to be thrusting the food inwards, towards 
the gape of the miindibles, at others to work up and"do\vn upon it, strained 
as it is between the third maxiliipeds and the mandibles, so as to cut through 
it. It is difficult to discover wliat is the work of the first maxilliped. The 
action of the gre:it lacinise would suggest that they are cutting the strand of 
food, but their armature of bristles is so .much feebler than the iirrangement 
of spines upon the dactylopodites of the second maxiliipeds and on the lacinise 
of the inaxillnle as to throw doubt upon the correctness of this impression. 
In view of the alternation of their action with that of the pyramidal endiles, 
it seems possible that they are really brushing the frayed portions and 
fragments of the food backwards towards the opening of the mouth, into 
wiiich the pyramidal endites help to thrust it. The shape of these endites 
and of the hairs upon them are such as to make it easy for the food to pass 
between them into the mouth, but difficult for it to emerge. The maxillse 
are, I think, quite useless as jaws. Their distal lobes, at least, are feeble, 
inefficient structures, drawn passively' to and fro with the strokes of the 
scaphognathite. I am less certain about the proximal lobes, but if these have 
a function I am unable to suggest what it may be. The maxillules are 
important and relatively powerful structures. I have described the 
movements of their hicinise. The outer of these cuts at the food with its 
powerful bristles and the inner, I think, thrusts it into th^ mouth. Probably 
in doing so it is cutting or tearing it from the main mass. The paragnathu 
appear to have the function of closing the notches on the hinder edge of the 
mandibles, through which the food might work outwards, and of pouring 
upon it the secretions of their glands, whatever be the functions of these. 
I have already described the working of the mandibles. I am unable to see 
that their "molar " faces have any grinding action^ but the)- appear to help 
to wall in the food which is being thrust into the mouth by the palps, and 
especially by the action and powerful nose of the labi'um. I have been a 
little surprised, in feeding to the crabs portions of fish and meat containing 
bone which I should have expected them to be able to crush, to observe that 
they were rejected, sometimes after being stripped of the softer tissues. It 
is quite possible, however, that in other circumstances these would have been 
devoured. After the meal a fiuriy of the mouth-parts is usually to be seen. 
* Possibly refle.ves from these limbs are needed to co-ordinate the raovements of the 
other mouth-parts. A prawn will ns readily take food from a pair of forceps as from lis 
own chelffi. A crab will not. 
