A new Species of Nectonemertes. 353 



The majority of these pass anteriorly, and branching repeatedly are 

 distributed chiefly to the body wall. Owing to the fact that branches 

 of one or two of these nerves are imbedded in the connective tissue 

 sheath surrounding the brain, they have been followed laterally 

 into close proximity to some of the more anterior reproductive glands. 

 A very few small fibres have their origin on the dorsal surface of 

 the brain (Fig. 6) and passing dorsally become lost in the somatic 

 musculature. 



On each side of the mid line and originating from the ventral 

 commissure at its junction with the brain, the proboscidial nerve 

 arises (Fig. 6), and pursuing its course dorsally for a short distance 

 divides repeatedly, and the resulting branches take their position 

 among the muscles of the proboscis sheath. As is shown in Fig. 7 

 there are 19 of tfiese nerves, which may be traced forward to the 

 rhynchodaeum where, having become smaller and united by a nerve 

 plexus, they disappear. Owing to the absence of the greater portion 

 of the proboscis nothing is known of its innervation. 



About one third the length of the animal from the anterior end 

 of the body the dorsal nerve becomes apparent and continues as a 

 conspicuous feature (Fig. 5, 13, 19) throughout the succeeding third. 

 Since this fibre has been found to connect with the dorsal brain 

 commissure in certain other nemerteans (cf. Burger's fig. 20, tab. 25), 

 it may exist in the anterior part of the body of the present species 

 in the form of a plexus, but it is to be noted that no nerve arises 

 from the mid section of the doi'sal commissure in Burger's figure 

 of a species of Carinella. Posteriorly the dorsal nerve graduallj'' 

 diminishes in size and finally becomes lost to view. 



Imbedded in the wall of the median blood vessel or in close 

 contact with it, is a delicate nerve which may be traced from a 

 point about 0,25 mm behind the brain to the posterior end of the 

 proboscis. Anteriorly it branches repeatedly and becomes lost in 

 the tissues of the proboscis sheath, while posteriorly it graduallj^ 

 diminishes in size and finally disappears. 



As the researches of Verrill have shown, the members of the 

 genus Nectonemertes are undoubtedly hoplonemerteans, but their more 

 intimate relationships are still uncertain although they have been 

 discussed by a number of authors. A few genera (Hyalonemertes, 

 Planktonemertes, Pelagonemertes) are now known which possess broad, 

 flattened more or less gelatinous bodies and the ability to swim, but 

 that they are necessarily closely related is by no means certain. 



