NEMERTEANS 



273 



Form and colour in life. The body is somewhat fusiform and in movement resembles 

 Oerstedia in its semi-rigidity. The tail is more pointed than the head. Eyespots are 

 visible in the smaller specimens. The colour is yellowish brown with a narrow median 

 ventral pale "sole". The larger worms are darker and show less of the mottling — light 

 irregular patches and dark spots — that is apparent in the smaller. There is a light ring 

 circling the body at the back of the head, usually behind the second pair of eyespots but 

 sometimes coincident with them. This pale annulation is characteristic of the species in 

 life. 



Form and colour of spirit specimens. Lengths 10 and 16 mm., breadths 07 and 

 1-4 mm. The body is nearly cylindrical, with the head thicker and blunter than the tail. 

 There is sometimes a complete annular groove at the back of 

 the head. The eyespots are not visible. The colour is usually 

 completely bleached, but occasionally sufficient brown re- 

 mains to display the white neck band. When cleared in anilin 

 oil the pigment shows as black specks. The eyes, which are 

 also rendered visible, are two pairs of brown cups, the con- 

 cavity of the anterior pair being antero-lateral, that of the 

 posterior pair postero-lateral. The eversible part of the pro- 

 boscis is less than half the length of the body. 



Anatomy. The epithelium is very thick. The relative thick- 

 ness of the body layers can be seen in Fig. 49. The head 

 glands fill the head completely and extend back on all sides 

 of the brain. Posteriorly they end dorsally with the dorsal 

 ganglia, but they continue beneath the stomach and anterior 

 caecum until the two forward diverticula of the latter join it. 

 The diverticula almost reach the brain. The proboscis is well 

 developed and possesses ten nerves. The armature consists of 

 a slim main stylet on a rounded base and two reservoirs each 

 with four, five or six stylets. 



The dorsal ganglia are small for the size of the brain and 

 the commissure is thin. The lateral nerves pass outwards and 

 up from the ventral ganglia and they each carry down the 

 body a strand of fibres from the dorsal ganglion. The cerebral 

 organs are very small and thin. They open laterally not far 

 from the head-gland pore and consist of a tube sheathed with large gland cells 

 extending a short distance behind the first pair of eyes. The excretory ducts open far 

 after the brain. 



The specimens taken in King Edward Cove in 1929 and 1930 came from a small red 

 alga. Three of these were found in mucous tubes attached to the weed. In 1929 four 

 brown worms within mucous tubes had been found attached to the rootlets of kelp and 

 described as N 50. On sectioning they proved to be Tetrastemma gulliveri. The epi- 

 thelium was torn off and the internal organs degenerated, especially the brain. The 



8-2 



Fig. 49. Tetrastemma gulli- 

 veri, Burger. Diagram from 

 a graphic reconstruction of 

 the head showing the eyes, 

 brain, cerebral organs, and 

 head glands. 



