214 REPORT 1851. 



dorsal to the ventral median line round the body. On the posterior side 

 this cirrus is protected and strengthened by a brush of strong bristles, which 

 are opened into a fan-like form also, fortifying thus the fleshy cirrus from 

 one edge to the other, and rendering an injury to it almost impossible : the 

 ventral foot is an exact repetition of the former. The setae present a very 

 apposite figure for aiding in progression (figs. 39 and 40). During the oar- 

 like motion of the foot from before backwards, the setae go before the cirrus, 

 protecting it thus from injury. The setae resemble the common oar in 

 figure, differing from this instrument only in having on either side of the 

 blade a membranous process, hooked slightly at the end towards the middle 

 piece or shaft (fig. 39). In virtue of this beautiful formation, the resistance 

 offered by the little oar to the surrounding element is so perfectly graduated, 

 that it slowly passes through the sand, while it forms the fulcral point of 

 motion ; the longer setae are simply blade-like (fig. 39, a). The foot, in being 

 carried forward to reperform the step, revolves slightly on its axis, and thus 

 feathers the setae, a manoeuvre by which resistance to progression is very 

 materially diminished. In Nerine, the tail in all species is a broad semicir- 

 cular and horizontal Jin, the anus being situated on its dorsal side. In con- 

 sequence of the vertical direction of the plane of the lateral fleshy appen- 

 dages, on that very account well qualified for aiding in progression through 

 loose sand, the animal is scantily and imperfectly pi'ovided with the means 

 of supporting itself in water ; under such circumstances the tail comes in as 

 an important instrument of locomotion. These observations are applicable 

 in every detail to the case of the larger species of Nerine, N. coniocephala. 

 This latter species differs from the former only in the structure of the 

 branchiae ; the other elements of the appendages are identically formed, and 

 the tail discovers the same ingenious construction. The author has added 

 another species of Nerine to those described, in which the fleshy cirri are 

 broader and larger, and better adapted for swimming, the tail having the 

 generic typical formation. There remains one remarkable and characteristic 

 feature of structure, with reference to the " appendages " in these eccentric 

 worms, to be noticed. All the species of this genus may be immediately 

 distinguished from all other Annelids by the extraordinary development 

 which occurs in the occipital tentacles. From the dorsal aspect of the first 

 or occipital annulus, two long tojoe-like appendages arise. In N. vulgaris 

 they equal in length one-third of the body ; in N. coniocephala they are not 

 so long, but stouter and stronger. 



In the new species to which allusion has now been made, these branchial 

 appendages extend as far as the middle point of the body, so remarkable are 

 they in length. The branchial appendages are true prehensile organs, used 

 almost exclusively in the search for food. On their under surface, in each 

 species, they are transversely roughened with angularly raised edges, these 

 again being armed by stiff gristly spinelets, a provision expressly introduced 

 for scraping, for which description of manual labour no implement yet con- 

 trived by the cunning of man can be better adapted. From the structure of 

 the soil, that of a shelly fragile loose sand, in which the lot of these worms 

 is cast, the perfect adaptation of these instruments to the end to be accom- 

 plished may be readily predicted. Their history in an especial manner exem- 

 plifies the rule, that even the humblest and meanest worm finds in its ap- 

 pointed habitat the conditions of prosperous and felicitous existence. 



Glycera, although an inhabitant of the shingly sand, has yet received a 

 special organization. It does not tunnel the soil into permanent subterra- 

 nean passages like the Nereids ; it struggles through the sand by the batter- 

 ing-ram operation of its proboscis. To the extremity of this vigorous organ 



