BORRADAILE— ON THE PONTONIIN^ 339 



The process of feeding has not been observed in Pontoniinse, and as yet we do 

 not even know upon what they feed, though it may be inferred that the species 

 which live in intimate association with sessile or subsessile animals probably share 

 the food of the latter, which consists of minute organisms swept up by ciliary currents 

 from the surrounding water. In regard to the use of the organs around the mouth, 

 something may be gathered from a study of the prawns of the genus Leander, in which 

 these organs are very similar to those of the Pontoniinee in their general structure 

 and arrangement. In Leander serratus there are bristles, borne upon ridges of the 

 coxopodite, basipodite, and ischiopodite of the first leg, which complete behind and 

 below the basket under the jaws, but which are less well-developed or absent in 

 Pontoniinae. Small particles of food may be seized and conveyed by the chelipeds 

 of either pair to the region of the mouth, where they are generally received by the 

 second maxillipeds, though sometimes they appear to be placed directly in charge 

 of more dorsally placed structures, probably the maxillules. A large morsel occasionally 

 appears to be steadied by the legs of the second pair, while those of the first pair 

 tear off fragments and carry them to the jaws, but it is more often placed as a whole 

 within the grasp of the second maxillipeds, which hold it in place while pieces are 

 torn off it by deeper-lying organs, probably in the main by the incisor processes. In 

 handling bulky masses of food the chelipeds are assisted by the third maxillipeds, 

 which bend back their last two joints for the purpose. The third maxillipeds are 

 also capable by the same action of scooping up food and unaided carrying it to the 

 second maxillipeds, between which they sometimes thrust it with their tips. During 

 these processes the basket appears to serve the purpose of keeping the food under 

 control till it has been seized by the second maxillipeds. These are very important 

 organs, and play an indispensable part in passing the food to the mandibles. The 

 animal can still feed if the legs and third maxillipeds have been removed, but if all 

 the other organs be left and the second maxillipeds cut away it is apparently incapable 

 of taking food. The second maxillipeds have three principal movements. In one, 

 the broad flaps in which they end open downwards like a pair of doors and with their 

 stout fringes gather up the food, in another they rotate in the horizontal plane to and 

 from the middle line, in the third the bent distal part of the limbs tends to straighten 

 so as to brush forward any object which lies between them. Frequently these move- 

 ments are combined. Once the food is past the portals formed by the second maxillipeds 

 its course is hard to trace, but the following seems to be its fate. If it be small in 

 quantity and finely divided, or very soft, it is abandoned to the action of the maxillules, 

 by whose strong, fringed lacinise it is swept forwards and probably caused to enter 

 the mouth chamber through the slit between the paragnatha*. If it be bulky or tough, 

 the second maxillipeds assist the maxillules in brushing it forwards towards the incisor 

 processes. The action of these latter is not so much a cutting one as a process of 

 tucking the food into the mouth chamber, by first backing outwards and then moving 



* Such is the impression made. But it may be that all food is worked into the mouth chamber by 

 the incisor processes, and that the function of the cleft on the metastoma is to enable the paragnatha to 

 part and give room for the admission of large pieces of food. 



43—2 



