146 A. J. CARLSON. 



8. The CepJialopods. - -Nerves to the cardiac apparatus of the 

 cephalopod molluscs have been described by Cheron (i866) r 

 Fredericq (1878), and Ransom (1884). Cheron worked on 

 Eledone, Octopus, Sepia and Loligo. In the Octopoda four nerves 

 are given off from the sub-cesophageal or pleuro- visceral gang- 

 lion. Two of these nerves pass to the stellate ganglia in the 

 mantle. The median pair of nerves takes a posterior direction 

 on the ventral surface of the liver and innervates the rectum, the 

 cardiac apparatus and the gills. At the level of the auricles is 

 found a small ganglion on each nerve, and from these ganglia 

 nerves are given off to the auricles and the systemic ventricle. 

 Further on their course each nerve sends a branch to the small 

 ganglion situated on the gill ventricle, while the main nerve trunk 

 enters the large ganglion at the base of the gill. According to 

 Cheron the arrangement is the same in the Decapoda, with the 

 exception of the innervation of the auricles and the systemic 

 ventricle. Cheron describes a commissure between the two vis- 

 ceral nerves a short distance in front of the systemic ventricle. 

 At the junctions of the commissure with the visceral nerves are 

 found ganglionic swellings, which he considers homologous with 

 the ganglia on the visceral nerves of the Octopoda which inner- 

 vate the auricles and the systemic ventricle. Fredericq and 

 Ransom worked on Octopus, but apart from their physiological 

 results they add nothing to the anatomy of the cardiac nerves as 

 given by Cheron. Neither of these investigators make any 

 mention of a commissure between the two visceral nerves similar 

 to that described by Cheron for the decapods, but Fuchs (1895) 

 figures such a commissure in Octopus. 



My own work was done on Octopus punctatns, Loligo pcalii 

 and Ommastrephes illcccbrosa. The innervation of the cardiac 

 apparatus in Octopus I found in all essentials the same as de- 

 scribed by the authors just referred to, and the reader is referred 

 to the figures given by them. In Loligo I found some relations 

 not described by Cheron, and the cardiac innervation of this ceph- 

 alopod will therefore be described with some detail. From the 

 median lobe of the pleural ganglion (PI. VII., Fig. 20) proceeds 

 a stout nerve, which as it penetrates the cranial cartilage sepa- 

 rates into two flattened branches running close to each other in 



