NEMERTEANS 289 



annulatus from the Cape of Good Hope (Stimpson) with Tetrastemma candidum, 

 although the latter was described under the name T. incisum. 



Dredging off the west coast of Africa was unfortunately not undertaken outside 

 Saldanha Bay. I should expect Baseodiscus delineatus to appear in the collection not- 

 withstanding its absence from the littoral fauna. 



The material from South Georgia and the Falkland Islands consists of sub-Antarctic 

 and Antarctic species peculiar to these regions ; with representatives of the genera 

 Linens, Cerebratulus, Amphiporus and Tetrastemma in great diversity and numbers of 

 individuals. The Paleonemertea are apparently not represented in the far south. Most 

 of the forms taken are widespread or occur in the catches as isolated specimens from 

 which no deduction as to distribution can be made. Linens longifissus is an exception. 

 This species was collected by H.M.S. 'Challenger' from a depth of 126 metres off 

 Marion Island and described by Hubrecht from one complete and one fragmentary 

 specimen. At St. 167 the R.R.S. 'Discovery' took this species again from a depth of 

 244-344 m - °ff Signy Island in the South Orkney group. This was perhaps the most 

 curious haul made, for at this one station two nets attached to the back of the trawl 

 produced between them twenty-five specimens. The same gear was used off South 

 Georgia, the South Shetlands and the Falkland Islands, but no other specimen was 

 captured. The only parallel instance that occurred among the Nemerteans was the haul 

 of seventeen Pelagonemertes rollestoni in one haul of the 4 \ m. net at St. 107. Pelagone- 

 tnertes, however, is a purely pelagic form, and swarming or "patchiness" in pelagic 

 animals is a recognized phenomenon, not necessarily connected with breeding and some- 

 times on a large scale (as in Enphansia superba), so that the two hauls are not really com- 

 parable. What is interesting is the connection of Marion Island with the Antarctic by 

 the occurrence of this species and of Amphiporus marioni, Hubrecht, now recorded from 

 South Georgia, just as Kerguelen is linked by Linens corrugatns, Mcintosh, and 

 Amphiporus moseleyi, Hubrecht, and both are separated from the northern continent by 

 the dissimilarity in their Nemertean faunas. Coe (1905, p. 77) suggested that ocean 

 currents with limiting climatic conditions are a factor, if not the factor, in the dispersal 

 of Nemerteans in the Bering Sea. Applied to the data given above, however, dispersal 

 by ocean currents does not seem a possible hypothesis, for it is difficult to understand 

 how the current which passes up the coast of West Africa could have influenced the dis- 

 persal of the northern littoral forms to the southward, or, supposing dispersal took place 

 in the opposite direction, why Linens corrugatus has not become established on the 

 West African coast with the help of the cold Benguela current. The facts indicate, I 

 think, a creeping dispersal along an unbroken coastline, or at any rate a line of shallows 

 with no extensive deep-water masses in the path of dispersal; and they suggest, in 

 addition, that both Marion Island and Kerguelen were once more intimately connected 

 with Antarctica than they now are. 



The stations at which pelagic forms were captured are shown in Fig. 66. The most 

 frequent capture was Pelagonemertes rollestoni, widely distributed in the South Atlantic 

 and Indian Oceans and also ranging north of the Equator. P. rollestoni has always been 



