226 THE APODID^: PART n 



and further, upon our homology of the large loco- 

 motory limbs with the first trunk limbs ; to this 

 latter point we shall return. In the meantime 

 we assume that these two reasons, taken together 

 with our whole argument, are sufficient to establish 

 the fact that the Trilobites possessed two pairs of 

 antennae like the Apodidae and the typical Crus- 

 tacea. 



FIG. 53. Rolled-up specimen of Calymene Senaria (after Walcott) ; the line through 

 the head is the line of the sections in Fig. 52. 



When now we come to ask how these antennae 

 were developed, we can only conjecture that in some 

 way or other they must have supplied the opening of 

 the oesophagus with jaws, or perhaps with simpler 

 instruments for pushing in food. It is improbable 

 that the first antennae should develop their ventral 

 parapodia as jaws, firstly because it is almost certain 

 that the original Annelid-Crustacean had already lost 

 all traces of the parapodia of the first segment, the 



