NEMERTEANS 



233 



numerous in the epithelium. Farther back on the body many of the subepithelial cells 

 stain with eosin. 



The rhynchocoel is long, but the proboscis is attached in the first half of the 

 body. 



Two vascular lacunae close to the rhynchodaeum can be traced back to the anterior 

 insertion of the proboscis. They reappear as a median lacuna ventral to the rhynchocoel ; 

 and from this lacuna arises the dorsal vessel and a dorsal lacuna which later divides into 

 two lateral lacunae in which lie the cerebral organs. Posterior to the brain the vascular 

 system has not been traced. 



The brain is very large (Fig. 10). There is a strong upper branch to the dorsal ganglion 

 posteriorly. This upper horn disappears before the lower, which is invested with the 

 cerebral organ and forms the posterior lobe of the brain. A dorsal nerve arises from the 

 dorsal commissure. On the intrusion of 

 the mouth the ventral ganglia separate and 

 from this point they may be called the lateral 

 nerves. Previous to this the ganglia are 

 close together and directly beneath the dorsal 

 ganglia. They curve outwards sharply to 

 take up their lateral positions. A pair of 

 nerves is given off before the separation for 

 the innervation of the pharyngeal muscles. 



The differences between these specimens 



and the worms described by Mcintosh 



(1873) are so slight that I have no hesita- 



v ' J/ .... _, „, Fig. 10. Cerebratulus fuscus, Mcintosh. Irans- 



tion in identifying them as C. fuscus. 1 he yerse section of the body at the extreme anterior 

 pigmentation is more distinct, but worms limit of the mouth, 

 of the same species even more distinctly 



marked have been described by Joubin (1894). Burger (1895) gives the body form as 

 characteristic— the tail being very wide. Evidently this is a variable character for 

 Mcintosh's description is "slightly tapered towards either extremity". The internal 

 structure bears out the identification, although I have not been able to find neurochord 

 cells in the ganglia. 



An autotomized specimen (N 129) of a small heteronemertean with a caudal appendage 

 was collected at Tristan da Cunha (St. 4). No colour note was made. The approximate 

 length was 30-0 mm. 



The body is round in section. The head is flat with long cephalic slits (3-0 mm.) and 

 a straight slit-like mouth 1-5 mm. long. The colour is uniformly greyish. The long pro- 

 boscis is protruded. The anatomical details of this form are interesting in that they are 

 definitely against the inclusion of this form with the Cerebratulus of the Falklands 

 (C. malvini). The peculiarly wide cephalic slits are present and the eyes, which are 

 absent in C. malvini, are here evident, confined however near the tip of the head. Well- 

 marked frontal organs are present. Head glands are very thin and scattered. The brain 



3-2 



