Gatty Marine Laboratory^ St. Andrews. 7 



branchiaft backward. Then the rings are marked by trans- 

 A'erse furrows, each being thus divided into two, whilst 

 further backward, as the space between the bristles increases, 

 into a larger number of rings. In some cases the posterior 

 lamellfB for the hooks are asymmetricab an intermediate 

 lamella occurring on one side only. The posterior segments 

 show less regularity in their narrow transverse dorsal furrows. 

 Posteriorly the body diminishes and ends in a terminal 

 anus. 



Behind the first distinct scute or ventral shield already 

 mentioned in connection with the mouth is a narrow elon- 

 gated one, followed by thirteen others, those immediately 

 succeeding the very narrow one gradually though slightly 

 increasing in antero-posterior diameter to the eleventh or 

 twelfth, whilst the last three or four are rudimentary, being 

 rounded or shield-shaped median elevations, gradually dis- 

 appearing to end in a moniliform and somewhat elevated 

 median ventral ridge, which by-aud-by is lost in the groove 

 posteriorl3^ 



The branchiae are three in number, of a fine dark red 

 colour, and slightly mottled under a lens. They coil and 

 twist actively under examination. The first is the largest, 

 the third the smallest. Each springs from a cylindrical 

 base, which soon divides dichotomously, though occasionally 

 a small tuft of three short filaments may be found on the 

 main stem of the first branchia. The terminal branches are 

 long and tapering, and in life these give the aspect of gills 

 formed of simple filaments. Each filament is enveloped in 

 a transparent structureless cuticle, whilst the centre is 

 marked by coherent granular tissue arranged in a close 

 series of transverse rows, so as to give the whole a finely 

 barred aspect. No distinct longitudinal fibres are apparent, 

 though in some a longitudinal canal is seen. In the basal 

 region are many large compound bodies, the " blood- 

 globules ^' of Williams. 



A small conical papilla situated in the groove close to the 

 exterior of the second pair of branchiae marks the com- 

 mencement of the setigerous processes, though it has no 

 bristles, and it is in a line with the second post-oral fold — in 

 the centre of which is the first small shield or scute. The 

 first bristle-tuft is opposite the last branchia, only a short 

 interval separating it from the base of the organ. It springs 

 from a setigerous papilla at the dorsal edge of the ridge for 

 the hooks. The bristles form a vertical row of considerable 

 depth, and in structure agree with the succeeding tufts, 

 no rudimentary forms marking the commencement of the. 



