NEMERTEANS 275 



branches of the anterior caecum (Fig. 50). The nephridial tubules open to the exterior 

 laterally at the level of the branches of the anterior caecum. The proboscis has ten 

 nerves and is armed with the usual main stylet and two reservoirs each with two, three 

 or four stylets. The brain is fairly large. The dorsal ganglia are smaller than the 

 ventral and there is no strand of fibres from the former to the lateral nerves. The 

 cerebral organs open ventro-laterally just in advance of the brain and pass inwards, 

 increasing in size and becoming applied to the brain between the dorsal and ventral 

 ganglia. 



One of my sectioned specimens was an immature male, the other an immature 



female. 



The identification of this form with T. hand, Burger, is based on the head glands and 

 the cerebral organs. Both of my series of sections show two short lateral diverticula 

 from the caecum. 



Tetrastemma longistriatum, n.sp. (Plate XVI, fig. 7; Fig. 51). 



This species occurred at the following stations. It was sketched and described under 



N48: 



St. 42. 1. iv. 26. OTL, 120-204 m. 2 (N 57). 



St. 141. 29. xii. 26. BTS, 17-27 m. 2 (N 48). 



St. 163. 17. ii. 27. BTS, 18-27 m - J ( N 9 1 )- 



11. iv. 27. Kelp roots, King Edward Cove, 2 (N 48). 



The lengths and breadths of some of the specimens were : io-o, 1 -o mm. ; 5-0, 07 mm. ; 

 5-0, o-6 mm.; 2-0, 0-2 mm. 



Form and colour in life. The body is round in section, tapering to the tail which is 

 much more acute than the head. There is a pair of deeply embedded eyespots just in 

 front of the head markings and another pair at the anterior end of the body pigment. 

 The ground colour of the body is pale yellow. On the back there are two longitudinal 

 brown bands, fading laterally, which leave a broad sharply defined streak between them. 

 At the head the streaks end, but there is a pair of very deep reddish brown patches on 

 the head in the form of two elongated right-angled triangles placed transversely, the 

 right angles being the inner anterior angles. 



Form and colour of preserved specimens. The length is about 5-0 mm., the breadth 

 0-35 mm. The body is cylindrical, the head blunter than the tail. The eyes are not 

 visible, but on clearing, the anterior pair are larger than the posterior. The colour and 

 markings are faintly seen. 



Anatomy. The most noticeable feature of the species is the extreme development of 

 the epithelium, which is at least twice the thickness of the remainder of the body wall. 

 It bears within its cells large masses which stain with haematoxylin. The head glands 

 are compact and solid masses opening just beneath the tip of the head. One strand 

 spreads over the rhynchocoel, just reaching the brain. Another forms a thick U-shaped 

 investment to the oesophagus but diminishes and disappears before the dorsal strand. 

 The lateral branches of the anterior caecum overlap the dorsal ganglia (Fig. 51). 



