Procephalic Lobes of Epeira Cinerea. 447 



The procephalic lobes lie not only above, but a little in front of, the 

 postcephalic ganglia (text-fig. 2). A large, almost tube-like, pair of 

 nerves, which are more dorsally placed than the others, extends from 

 the brain to the anterior median eyes. The nerves supplying the 

 posterior median eyes arise from the surface of the brain near those 

 which supply the anterior median eyes, and follow almost parallel 

 M'ith them, though occupying a somewhat lower level. The nerves 

 which supply the lateral eyes arise from a more lateral position on 

 the side of the brain, in conjunction with the lateral optic vesicles. 



The remaining nerves are all given off from lower levels. They 

 consist of a fine strand of nerve fibers which arises in the median line, 

 between the optic lobes, and passes to the rostrum ; and the cheliceral 

 nen^es, which arise from the upper part of the connectives, or ganglia 

 of the cheliceral segment. 



The mandibular and pedipalpal nerves arise from different levels 

 of the pedipalpal segment. The remaining portions of the post- 

 cephalic ganglia give off, on each side, the four large nerves which 

 pass to the appendages. The nen^e cord consists of two large, tubular 

 nerves which arise from the dorsal surface of this portion of the 

 brain. 



Between the appendicular nerves are four pairs of fine, thread- 

 like, accessory, or segmental, nerves on each side of the brain. These 

 nerves supply the thoracic muscles and the body wall. The nerves 

 comprising the first segmental pair are fused, although they separate 

 into two branches a short distance from their point of origin. 



The paired condition of the segmental nerves does not appear in 

 the scorpion according to McClendon (26), although Patten, who 

 studied the same species, seems to have had no difiiculty in making 

 them out. 



VI. The Eyes of ErEiRA. 



No problem in Arthropod enilu'vcjlogy has attracted more atten- 

 tion, or yielded more interesting results, than the study of the devel- 

 opment and relationships of the eyes of Arachnids. The most 

 important of these observations are to be found in papers by Bert- 

 kau (4), Schimkewitsch (28), Locy (23), Mark (25), and Pat- 

 ten (33, 35). 



