54 W. MILNE ON THE 



The nibbling, pecking action would be produced by the shooting 

 forward of the two halves towards d, without any rotation or 

 alteration of the direction of the planes a c e e^\ and then 

 reversing the action. The rod ah has considerable freedom 

 at the point h. 



The second action seems to be produced in something like the 

 following way. When the rods ae are pushed inwards and 

 downwards, the rami ce^ will bear on each other at the top ends, 

 and as the pushing is continued will rise upward and forward — 

 acee^ being rigid planes — and h will be shot forward towards 

 d ; the whole action producing a grinding, rotating and forward 

 movement at the fi'ont of c e^. The point e in the above action 

 apparently approaches e^ but does not in reality, for as e goes 

 down e^ rises, giving the rotating movement which would not 

 be possible if the planes a c e e^ were not rigid. 



When the reverse movement takes place, 6, 6 may be brought 

 down as far as to bring the unci in a straight line, throwing par- 

 ticles that may have been caught on to the grinding surfaces of 

 the front ends of the rami and possible parts of contact below. 



It seems to me that there are here all the elements of the 

 Philodina jaws. The two halves of the jaws of M. falcatus re- 

 present the framework of the Philodina subquadrate parts ; 

 all the evolution required would be a thickened margin to the 

 glassy plate between, and soldered on to e and e^ ; the joints 

 in the mallei soldered ; the rami and unci points muscularly con- 

 nected ; and the minute rods thrust under, and thus taking the 

 position of the double fulcrum in the Philodina jaws. 



In the Philodina jaws the only parts soldered together at the 

 front and back of each half are the borders of the surface which 

 carries the teeth, they at least appear so. The ends of the 

 rami are only muscularly attached. I can find nothing at all 

 that could be considered a fulcrum where Gosse (1) represents it 

 to be. The fulcrum of Ploima is represented here by two chisel- 

 faced teeth (PL 3, fig. 3e) opposing each other, one on the keel 

 of each ramus about one-third back from the anterior. Strong 

 muscles connect them with the front of the jaws. The outside 

 borders of the surfaces carrying the teeth and the striae are the 

 mallei, and the inside opposing faces, each of which appears some- 

 what like a triangular file in shape, represent the rami. Round 

 the jaws are three great muscular masses, two from the front 



