. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 244 DISCOVERY REPORTS muscles. Glandular tissue encloses the canals and a nerve from each dorsal ganglion passes into the organ. The dorsal ganglia are smaller than the ventral. There are ten nerves in the proboscis. No excretory vessels or ducts could be traced. The armature consists of a main stylet on a base somewhat longer than itself and two accessory reservoirs. In one worm three accessory stylets were present in each reservoir but in others there were only two. The lengths were as follows
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 244 DISCOVERY REPORTS muscles. Glandular tissue encloses the canals and a nerve from each dorsal ganglion passes into the organ. The dorsal ganglia are smaller than the ventral. There are ten nerves in the proboscis. No excretory vessels or ducts could be traced. The armature consists of a main stylet on a base somewhat longer than itself and two accessory reservoirs. In one worm three accessory stylets were present in each reservoir but in others there were only two. The lengths were as follows: Main stylet 0-067 mm-> accessory stylet 0-058 mm., base 0-077 mm- This species appears to correspond with Tetrastemma incisum, Stimpson (1856). I can see no reason for separating it from T. candidum, Muller, since in size and shape of the body and head, and in the absence of markings it agrees closely with a colour variant of this species. Tetrastemma nigrolineatum, (Plate XV, fig. 9; Fig. 17). A single specimen was taken in July from a kelp root inside the Bay. The length was 25 mm., breadth about 0-3 mm. This slender worm appears to be rectangular in section, and the head is wedge-shaped when seen from the side. There are no eyespots and neither mouth nor cephalic slits are visible. The colour is whitish green, with two parallel black lines passing down the back from tip of snout to tip of tail. At the head these lines are thinner than they are on the body. In spirit traces of the double dark line can be seen. Internal structure. Head glands are absent. The epi- thelium is about as thick as the longitudinal muscle layer. The basement membrane and circular muscles are thin. The former is thinner than the latter and stains with haematoxylin. Brown pigment granules are present at the base of the epithelial cells where the dark lines can be seen in life. There are no traces of eyespots. The oesophagus opens into the rhynchodaeum, and the common pore is ventral to the t
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