1902.] ON THE ANATOMY OF THE PEDIPALPI. 169 



4. On some Points in the Anatomy of the Alimentary and 

 Nervous Systems of the Arachnidan Suborder Pedipalpi, 

 By R. I. PococK, F.Z.S. 



[Received May 30, 1902.], 

 (Text -figures 40-45.) 



1 . The Nervous System of the Opisthosoma in the Thelyj^honidse. 



Accoi-ding to Blanchard ^ the opisthosoma of Thelyphowas is 

 innervated as follows : — Fi'om the postaxial side of the trunk 

 supplying the sixth apjjendage of the prosoma springs a nerve 

 which passes backwai'ds parallel to the median coirl into the 

 pregenital somite, giving off a slip to the muscles of that limb. 

 Towards the>posterior end of the prosoma, the median nerve-cord, 

 which is described as single, sends off on each side a nerve which 

 traverses the pi'egenital somite and divides into two branches, 

 one for the first or genital somite, the other for the second 

 somite. The nerves supplying the third, fourth, fifth, and sixth 

 somites spring f I'om a common centre, forming a minute ganglionic 

 swelling on the median cord in the anterior poi'tion of the genital 

 somite. In the seventh somite the median coi'd forms a relatively 

 large ganglion, whence five nerves radiate to the five posterior 

 somites of the opisthosoma. 



Blanchai'd's observations were based upon a species from 

 Martinique, now known as Mastigoproctics antillensis. I have 

 had no opportunity of dissecting specimens of this species. I find, 

 however', a very diffeient state of things in a Bui-mese species, 

 Hypoctoivus formosus. In the first place, the median cord is not 

 single, but double. In the second place, it gives off no nerves 

 between its point of origin at the posterioi- exti-emity of the 

 suboesophageal mass in the pi-osoma and its ganglionic enlaigement 

 in the seventh somite of the opisthosoma (text-fig. 40, A, 7n.n., 

 p. 1 70). All the nerves which originally emanated from it to supply 

 the pregenital somite and the anterior six somites of the opistho- 

 soma have passed foi-wards and become united to the ganglionic mass 

 of the pi'osoma. They form on each side a compound sti'and lising 

 between the median nerve-cord and the nerves of the sixth 

 appendage (text-fig. 40, A, op.n., p. 170). Running backwards for 

 a short distance, pai'allel with the median coirl, and giving off a 

 slender nerve to the muscles of the sixth appendage, they soon 

 dip beneath the coi-d and meet in the middle line in the narrow 

 channel between the coxa? of the appendages of the fifth piiir. 

 Posteriorly from this point the two cords extend side by side 

 along the sternal surface of the body, beneath the double median 

 strand. The nerve to the genital somite rises in the posterior 



1 Org. du Regno Anim., Avacliu. p. 152, pi. viii. fig. 4. 



