202 BULLETIN OF THE 



The anterior end (Figs. 5, 6, 7, 8) is blunter than the posterior (Fig. 10), 

 and in cue specimen has a clear cavity within, easily ^een through the cephalic 

 walls, in which, as Verrill has already mentioned, four transparent, nucleated, 

 cells lie. The mouth cannot be observed very distinctly, but is discovered by 

 close observation on the ventral side of the head as a narrow longitudinal* slit. 

 There are no cephalic tentacles or other appendages to the head. A pigment 

 spot was noticed in the walls of the head just in advance of the transparent 

 region, but whether it is an ocellus or not was not determined. The digestive 

 tract, which is of varying diameter, but always small as compared with that of 

 the body cavity, extends from one extremity of the crown to the other. The 

 walls are muscular, and at times have a rhythmic pulsatile motion, which may 

 be seen through the body walls. The anus is terminal, and mounted on a 

 curved caudal prolongation of the body, slightly enlarged at its extremity. 

 According to Prof. Verrill the posterior end of the male and female Nectoncma 

 differ from each other, and he speaks of a peculiar " papilla " found in this 

 region of the female. 



The stomach and intestine often become so inflated that they fill the body, 

 so that they cannot be distinguished from those of the body cavity. The 

 "yellowish white organ [ovary?] extending from near the head to the tail," 

 mentioned by Prof. Verrill, was observed in one specimen. 



The affinities of this singular worm with known genera are somewhat doubt- 

 ful. Prof. Verrill, with an implied expression of doubt, refers it to the Nema- 

 todes. That reference seems to me a proper one, but from what little is known 

 of its anatomy it can find few near relatives among the genera now known in 

 this group of worms. It must, if a Nematode, take its place near tlie Cha'toso- 

 midce, or j^erhaps by the side of that strange worm Eubostrichus, of even more 

 problematical affinities, described by Greef,t from the North Sea. If near the 

 latter, it is as a giant with a pygmy, for Eubostrichus is but 8 mm. in length, while 

 Nectoncma is ten times as large. The matted covering, formed of hairs, which 

 characterizes Eubostrichus according to Greef, does not exist in Nectoncma. 

 There is, however, a tendency for something like this covering to form on the 

 hairs along the lateral lines. Nectoncma is a genus with close affinities on the 

 one side with the Nematodes, while on the other it presents strongly marked 

 Chajtopod characters. The segmentation so pronounced on the lateral bands, 

 and the douUe row of hairs upon the sides, point to the Annelides as its near- 

 est allies. The connecting web of the lateral hairs recalls the lateral fins of 

 Sagitta. 



* In Prof. Verrill's specimen, " a transverse whitish band seemed to indicate the 

 position of the mouth." 

 t Arch. f. Naturg., 1860. 



Cambridge, December, 1883. 



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