42 THE VOYAGE OF H.M.S. CHALLENGER. 



amongst the Challenger Nemertea. I have already indicated (p. 37) why I wish to bring 

 it under the genus Cerebratidus, rather than under Linens, where M'Tntosh placed it. 



The following notes were made by him concerning the Challenger specimens. 



" Dredged in considerable abundance in Royal Sound, Kerguelen, January 27, 1874, 

 in 25 fathoms. 



"Stat. 149, off Christmas Harbour, Kerguelen, 120 fathoms, small specimens. 



" Stat. 151, off Heard Island, 7th Febr. 1874, 75 fathoms. Some reach the length of 

 200 mm., and much contracted forms have a diameter of about 15 mm. In the oesophagus 

 of one was a blackish mass of sand-grains, sponge-spicules, Diatoms, and mud." 



In M'Intosh's. previous publications the description of Lineus (Cerebratulus) corru- 

 gatus contains the following characteristic features : — 



"Body rather abruptly pointed anteriorly, and more gradually posteriorly. The 

 oesophageal region is marked externally by a series of prominent and somewhat regular 

 rugae, which sweep from the mouth dorsally and ventrally. 



" Colour dark olive throughout, with the exception of a white band, which crosses the 

 anterior border of the snout, and passes backward to the posterior third of the lateral 

 fissure, where it bends dorsally and terminates." 



" The special characters are the very large mouth, with the prominent rugse, which 

 show that the ammal probably possesses unusual powers of oesophageal protrusion — a 

 supposition borne out by the great development of the external circular muscular fibres, 

 the dorsal longitudinal coat, and the other fibres of the organ. The internal glandular 

 lining is also very firm." 



A couple of figures are added, one a section of the proboscis, the other a section of the 

 ventral body-wall. The latter should be compared with our fig. 6 on PI. XIII. It will 

 then be seen that M'Intosh's " pigmentary layer, divided by a definite black band," is 

 our superficial and deeper layers of the integument (Isg and Idg). The " black band" 

 between them is no other than our external secondary basement membrane. What 

 MTntosh designates as the " curious translucent stratum cut into somewhat regular 

 spaces" is our basement layer proper (B), comparable to that of Eupolia and Garinina, 

 and radially traversed by bundles of contractile and nervous fibres, which bring about the 

 "regular spaces" alluded to. 



On the whole, our two figures will be seen to correspond very well, only M'Intosh 

 omits the nervous layer and the innervation of the oesophagus. The large mouth and 

 folded lips were very conspicuous in the Challenger specimens, the head of one, seen from 

 the ventral surface to show the mouth, being figured on PI. XIII. fig. 5. 



The different series of sections which I have made through four specimens of Cerebra- 

 tulus corrugatus were very instructive in several respects, although they all conform to 

 the well-known Schizonemertean type. It is especially the considerable development of 

 basement tissue of the integument (PI. XIII. fig. 6, B), which not only brings out the 



