GIG.IXTOCYPRIS MULLERI 



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second to fifth and then runs downwards with the outer group of sixth to eighth dorsal 

 longitudinal muscles in the afferent channel of the pericardium. Just below the point 

 where the three outer muscles twist over each other (p. 215) the nerve divides into two 

 branches, one continuing downwards as the posterior cardiac nerve in the afferent 

 channel and the other passing through the pericardial floor close against its anterior 

 attachment to the body wall. The latter I call the anterior cardiac nerve. It runs 

 downwards towards the adductor tendon and receives a branch from the shell near the 



Fig. 15. Drawing of a thick section passing through the single cardiac neurone and the pair of hepatic 

 valves, c.n. cardiac neurone; e.n.c. efferent cardiac nerve; h.v. hepatic valves; pc. pericardium; pc.d. peri- 

 cardial dilator. 



bottom of the isthmus, the fourth shell nerve. It then runs as the combined anterior 

 cardiac + shell nerve IV down the tendon of the dorso-ventral body retractor muscle 

 (Figs. 6, 14) to loop under the adductor tendon and enter the nerve ring on the dorsal 

 side of the maxillulary group (Fig. 11). The anterior cardiac portion, as it passes down- 

 wards, gives off small branches which can be traced to their nerve endings on muscles 

 4, 5, 11 and 10 (Fig. 9). 



The posterior cardiac nerve continues down the afferent channel to a point near the 

 lower ends of the outer dorsal longitudinal muscles. Here it receives a large nerve 

 from the dorsal body wall — the pericardiac nerve. This I have traced spreading out over 



