364 Introduction to Animal Morphology. 



nal ganglia, the last of which sends two branches to 

 the end-claw of the tail. 



Galeodes and Phrynus have two pharyngeal ganglia, from 

 the hinder of which two medio-ventral cords pass to the so- 

 mites, forming one posterior abdominal ganglion (often re- 

 presented by a commissure), and two ventral cords, with a 

 ventral ganglion. Pycnogonum and Tardigrades have four 

 nearly confluent ganglia in the ventral cord (more separate in 

 Nymphon). In Scorpions and Epei'ra a visceral nerve springs 

 from the brain, and passes along the oesophagus, on which it 

 forms a ganglion. In Opilio the visceral nerve comes from 

 the ventral ganglion, and forms many small ganglia. A simi- 

 lar nerve exists in many spiders. 



There are no special organs of touch, of smell, nor 

 of hearing. The eyes consist of clusters of crystal 

 rods, largest in Lycosae, covered closely with a con- 

 vex corneal-lens. Pigment surrounds the cones in 

 spiders, sometimes forming a tapetum, and even a ring 

 or iris in front, around the surface of each cluster, 

 along the margin of the cornea lens : in this are im- 

 bedded circular muscular fibres in some species. 

 Scorpions have two large eyes close together, and 

 laterally a group of 2-7, smaller. In Spiders there 

 are eight in two rows. In Opilio there are three or 

 four. Pycnogonum has four ; others have two, and 

 Pentastomum none. In some species of Trombidium 

 they are stalked. The skin is generally soft, sensi- 

 tive, never completely calcified, usually beset with 

 hairs or bristles, rarely with scales ; sub-dermal glands 

 sometimes exist, as the two lateral organs of Adeno- 

 pleura. The muscles of the body are yellowish, and 

 remarkable vertical bands pass between the viscera, 

 which they hold in their place. These fibres can make 



