76 THE APODID.^ part i 



Annelid, Wc may perhaps find some support for 

 this view in the fact that the first antennae never 

 appear in the Crustacea as anything but uniramose 

 which shows that, in the original Annelid, they had 

 long lost all traces of the parapodia to which they 

 primitively belonged, and were nothing but sensory 

 organs projecting forwards on each side of the pro- 

 stomium. 



Some further light might perhaps be thrown on this 

 point by a study of the central nervous system of 

 Limulus, which shows in some respects a more primi- 

 tive condition than that of Apus, at least as regards 

 the position of the brain. According to Packard, the 

 fibres of the first antennal nerve do not come from the 

 brain, but from the oesophageal commissures near it. 

 Owing, however, to the great modification of the 

 oesophageal commissures of Limulus, in consequence 

 of the lengthening out of the oral aperture, it is doubt- 

 ful whether this fact supports the view illustrated in 

 Fig. 20, that, in the original Annelid, the ganglia of 

 the antennae had moved to near the brain. 



There are, however, other points which bear on this 

 question. On examining the first section of the ven- 

 tral cord of Apus, we find a long ganglion consisting 

 of two groups of ganglion cells, and joined by two 

 transverse commissures. From the long ganglion, the 

 prostomial-oesophageal commissures run down to 

 embrace the oesophagus. Before reading Pelseneer's 

 paper, we were inclined to consider the front group of 

 ganglion cells, which form part of the long ganglion, 

 as belonging to the first antennae. It did not occur 



