344 ME. H. M. BERNAED ON THE 



The heart is very richly supplied with nerves. In portions of that organ dissected 

 out, cleared, and examined in toto, it seems to be enveloped in a network of nerve-fibres 

 which is especially developed in its dorsal wall. Pig. 7, PI. XXXIV., is a small portion 

 of the heart (ventral aspect) showing a layer of nerve-fibres (w) running longitudinally. 

 The exact source of these heart-nerves I have been unable to discover. 



A not very close network also surrounds the digestive tubules of the mid-gut, the 

 main canal of which is very richly supplied anteriorly, apparently direct from the brain, 

 but posteriorly also from the great abdominal nerve (PI. XXXI. fig. 6, ah). 



The Abdominal Ganglion. — The abdominal ganglion lies just above the genital aperture, 

 and in all probability supplies it with nerves, although the genital glands themselves 

 have their own independent nerves coming direct from the central nerve-mass. 



It is possible that this position of the abdominal ganglion may be due to the abdominal 

 musculature, which is only developed to any great extent in the first two or three 

 abdominal segments {cf. p. 336). 



The nerve which in other Arachnids is of importance for comparison is the abdominal nerve, as its 

 ganglionic svpellings may be primitive ganglia of the ventral nerve-chord which have persisted as separate 

 centres, and have not beeu incorporated in the cephalothoracic nerve-centre. 



In the Aranese there are no large swellings on the abdominal nerve. In this group, as we have 

 seen, the posterior median component of the central nerve-mass appears to consist of five or six 

 fused segmental ganglia, i. e. if the connective-tissue strands which penetrate it dorso-ventrally represent 

 primitive divisions. 



In Phrynus, also, there are apparently no ganglionic swellings in the abdominal nerve. 



The same is true of the Pseudoscorpions. 



In Thehjphoims there is a large svpelling at the posterior end of the abdomen, apparently in associa- 

 tion with the muscles for elevating the three tail-segments and for moving the caudal appendage. 



In Phalangium a ganglionic swelling is figured by Blanchard. This may be in association with the 

 highly specialized ovipositors and penes, with tbeir own musculature, which characterize tliis group. 



In Scorpio, in which animal alone the musculature of the abdomen is highly developed, there are 

 seven ganglionic swellings of the abdominal nerve *, which may again be associated with the developed 

 musculature for the movement of the tail-segments. 



The "Sympathetic." — The only other nerves to which I should like to refer are the "sympathetic." 

 Both St. Remy t and A. Schneider J describe a stomatogastric nerve as branching off laterally from the 

 brains of Spiders. Schimkevitch also describes a pair of nerves proceeding backwards from the brain, 

 but, like myself, failed to establish their places of origin. Blanchard figures nerves running backward 

 from the brain on to the mid-gut of Galeodes, and scattered nerves running backward on to the mid-gut 

 from the brain of Mygale. I have myself, as above stated, failed to find any clear connection between 

 the brain and mid-gut in either Galeodes, the Spiders, the Scorpions, Pseudoscorpions, or Opiliouidse. 

 Although the brain is, in all or nearly all cases, in contact with the mid-gut and its lobes, until I read 

 the works of St. Remy and Schneider I had concluded that the nerves leave the posterior surface of 

 the brain and spread out over the mid-gut, not in definite bundles, but as single fibres, which easily 



* Cy. Newport (58), "On the Nervous System, &e., of Macrourous Arachnids," Phil. Trans, vol. cxxxiii. 1843^ 

 and Blanchard (24), ' Les Arachnides.' 



t St. Eemy (61), ' Contributions u I'Etude du Cerveau chez les Arthropodes tracheates,' Poitiers, 1890. 

 J Schneider (64), '> Systiime stomatogastrique des Aranoides,'" Tab. Zool. ii. 1891. 



