PANTOPODA 



423 



The 2d pair of extremities is generally shorter than those which follow, 

 and in several genera is wanting. The 3d pair of extremities is 

 developed in the males of all Panfopoda, and functions in them as 

 egg-carriers. In several genera it is wanting in the females. The 

 extremities 4-7 are never absent, they consist of nine joints, and 

 end in claws, and are in comparison with the body exceedingly 

 long, giving the animal a spider-like appearance. All the extremities 

 are uniramose. 



The nervous system in the adult animal consists of a supra- 

 cesophageal ganglion, an oesophageal commissure, and a ventral chord. 

 The latter has 4 or 5 pairs of ganglia, from which arise the nerves 

 for extremities 2 - 7 ; it ends posteriorly with one or two pairs of 

 reduced ganglia, the last of which gives off nerves to the abdomen. 



FIG. 288. Nymphon hispidum, male, ventral side (after Hoek). The setae are omitted. 

 1-7, Limbs ; (1, chelicerae ; 3, egg-carriers) ; s, proboscis ; ab, abdomen. 



Since the most anterior ganglion of the ventral chord consists of 

 2 or 3 pairs of ganglia, distinct in the larva, the complete number 

 of the pairs of ganglia in the ventral chord is 8, 7 of which 

 belong to the trunk and 1 to the abdomen. According to this the 

 number of trunk segments and also of pairs of limbs must originally 

 have been 8. From the supra-cesophageal ganglion the nerves for the 

 eyes arise, and also those for the first pair of limbs and some of those 

 for the proboscis. Some of the other proboscis nerves have their roots 

 in the anterior portion of the first ventral ganglion. The nervous 

 system of the proboscis with its ganglion is very complicated. 



Four eyes, each with a cuticular lens and a retina surrounded by 

 pigment, lie on a prominence on the dorsal side of the first trunk 

 segment. 



The enteric canal has 3 divisions : fore-gut, mid-gut, and hind-gut. 

 The fore-gut, placed in the proboscis, has a complicated inner frame- 

 work and a "fish trap" apparatus. The straight mid-gut is provided 



