326 MR. CYRIL CROSSLAXD OX THE [Feb. 16, 



baisses " winch Claparede mentions and figures (pi. 2. fig. 5 d). 

 Pei'haps these oi-gans are eversible, or have here become hyper- 

 trophied. 



The means by which the long and tortuons burrows are made 

 are still unknown; the principal suggestions being (1) by aid of 

 .an acid secretion, (2) by the mechanical action of the jaws. While 

 in the Maldives, Gardiner repeatedly tested the effect of the 

 bodies of boring annelids upon litmus-paper without finding any 

 acid reaction, a result identical with Mcintosh's obsei'vations on 

 Polydora^' . Indeed, it is not easy to see how an acidity of the 

 body could produce any effect beyond enlarging the diameter of the 

 burrow, which is never found larger than the body of the worm 

 it contains. The supposition that an acid secretion aids the action 

 of the jaws is negatived by the calcareous composition of the 

 lower plates, the only parts the action of which could conceivably 

 produce the results seen. The size and gouge-like shape of these 

 strongly suggest their use in cutting out the canal by a rotary 

 motion' of the head. The softness of ordinary reef-rock and the 

 porous natuie of coral make this hypothesis a possible one. 



The mode of life of this species would, if known, be of great 

 interest. Is it usually possible for the head to come to the 

 surface to seek food, or does it, as seems physically necessary, and 

 as is indicated by the absence of gills anteriorly, remain usually 

 at the deep end of the burrow ? Can the boring sponges and algae 

 parasitic in corals afford an appreciable amount of nutriment to 

 the woi'm ? 



Genus NiciBiON Kbg. 

 As Eunice hut without gills. 



The species of this genus are but few in number, and several 

 of the names apply to species not yet properly described. Of 

 Kinberg's three species iipon which the genus was founded, two 

 are very probably, as Grube notes, specimens of E. sicilie^isis ; but 

 the third N. cincta, which possesses acicular setfe, is probably a 

 triie Nicidion, and the shortness of its tentacles indicates the pro- 

 bable identity of this Pacific form with that from East Africa. 



The species of which certain identification is possible are but 

 four in number, viz. : — 



N. kinbergi H. E.Webster, Bull. U.S. Nat, Mus. 25, 1884. 

 iV. balfouriana McI., 'Challenger Reports,' xii. 1885. 

 A\ brevis Ehl., ' Florida Anneliden,' 1887. 

 ^A^. ede^itulitm Ehl., Die Polychaeten des magell. und chil. 

 Strandes, 1901. 



Of these K. edentulum is distinguished from all the other species 

 * Annals & Mag. N. H. ser. 4, vol. ii. p. 276 



