19 



such organs as have been just described, lend considerable support to 

 the view that the half-labrum and its appendages are the equivalent of 

 of the Crustacean antennule. 



The central portion of the epipharynx is occupied by a U-shaped 

 rod, closed-in in front by a second pectinated rod, the posterior comb. 

 Within this enclosed region are two bunches of slender chitinous hooks, Grappling hooks. 

 the grappling hooks. Each bunch contains about eight hooks, which 

 pass forwards and outwards and then curve downwards outside the 

 U-shaped rod. Below the U is a small slightly chitinous plate. The 

 two bunches of hooks can be entirely withdrawn within the U, or 

 protuded so as to form a rake-like organ. The claws are moved by 

 powerful muscles, and when these are set in action the various parts of 

 the epipharynx change their positions and appear so different, that it is 

 difficult to discover what has taken place, and quite impossible to explain 

 the changes. 



If we compare the toothed feelers, the tentacles and the combs, we Similarity of 

 find that they can be all reduced to one pattern, a rod-like process *lers,tentacles 

 with irregular outline towards the free end ; the tentacles are in fact 

 feelers very minutely toothed. In the combs the change is somewhat 

 greater. Each comb is really composed of two chitinized feelers bent 

 over on their sides until they just meet in the middle line, while the 

 toothed surface, here entirely confined to one side, takes the form of a 

 stiff fringe of spikes, the two together having a most comb-like 

 appearance. This can only be made out under the most favourable 

 conditions. The labrum may truly be described as a sensory-motor 

 equipment of remarkable complexity. 



The mandibles are the most densely chitinous portion of the head, The Mandibles. 

 quite black and opaque at the tip. Each shades off into translucent 

 brown at the base, where it articulates with the epicranial plate behind 

 the antennal boss. The distal half of the mandible is toothed on the 

 inner side and fringed with stiff curved hairs. The proximal portion 

 is broader especially on the ventral side (compare fig. 7 with fig. 6) and 

 the inner surface is somewhat concave ; from the dorsal side of the 

 cavity a curious arborescent hair arises with three main branches and 



