246 



A. IZUKA. 



ncctive [ac. ces. e.). This represents a strong nerve, but is not so thick as 

 the one preceeding it. At the roots the two connectives of each side are 

 in contact, but laterally they slightly diverge so as to run apart of each 

 other. Arrived at the base of the posterior tentacular cirri, the accessory 

 connective swells up into a terminal ganglional knob, the posterior 

 cirrus ganglion before alluded to (/>. c. g.) Besides standing in con- 

 nection with the anterior cirrus ganglion as already mentioned, this ganglion 

 sends off two nerves which supply the posterior pair of tentacular cirri. 



The two pairs of (esophageal connectives with cirrus ganglia 

 essentially agree in their arrangement with the same in Nereis In N 

 regia* and N. virens\ there should occur about midway in the course of 

 each accessory connective a ganglion which however seems not to have been 

 seen by EhlersI! in N. eiiversicolor . No trace of the ganglion is present in 

 Cereitocepliale osaiveti. The same commissural nerve connecting the anterior 

 and posterior cirrus ganglia as that observed by me in the present worm 

 had been figured by Turnbull for N. virens ; but it apparently was not 

 found by Quatrefages and Vaillant in N. regia, nor by Ehlers in the 

 species studied by him The points here referred to seem to be subject 

 to much variation according to species 



Behind the two pairs of oesophageal connectives and from the region 

 adjoining the first ganglion (in the second and third body-segments) of the 

 ventral nerve-cord, the infra-oesophageal ganglion gives off, sym- 

 metrically on both sides, three more pairs of nerves Of these the first 

 and the second pair consist of slender nerves, the termination of which I 

 have not been able to make out. The third pair is the parapodial nerve, 

 the same as that which occurs in every, more posteriorly situated body- 

 segment ; it innervates the first parapodium, i. e., the parapodium belong- 

 ing to the second body-segment. 



Beginning with the third body-segment, the ventral nerve-cord sends 

 forth, in each of the successive body-segments, four pairs of lateral nerves, 



* Quatrefages et Vaillant. — Histoire naturelle dis Annelés. 1S65. 



t F. Turnbull. — On the Anatomy and Habits of Nereis virens. (Trans. Connect. Acad. Arts 



and Sciences 1876. Vol. III.) 

 Il E. Ehlers. — Die Borstenwürmer. 1S68. 



