Gutty Marine Laborat >ri/j St. Andrews. 153 



lon^ vase witli a tailoring process on tlie lip, or the filament 

 had a blunt clavatr tip or a cone at the end. lu another 

 instance (197 metres) \\\ which no operculum was present 

 the tips of the two dorsal fihuueuts were simply flattened and 

 wider than the rest. Accompanying the foregoing were 

 several — it may be young forms — in which tlie tips of the 

 tilauients were short and little tapered. The presence or 

 absence of opcrcula, indeed, would appear to depend on no 

 reliable data. 



Variability is not confined to the tips of the branchial 

 filanients, for the pinniL' are short as in the young budding 

 forms from Plymouth, or of great jjrcportional length as in 

 c rtain forms from the North Sea, the branchial fans of 

 which, moreover, are about half the lengtli of the body. The 

 pinnje of these are much longer and more slender than in 

 any from Plymouth, thougb the age of the specimen has 

 considerable influence in this respect. 



The number of the bristle-tufts in the anterior region is 

 likewise variable — ranging from five to ten, though a coi:- 

 siderable majority show seven, the number most frequent 

 in the north. 



The first pair of bristle-tufts, the collar-bristles, diverges 

 from the others in size, direction, and structure, and iii 

 these respects is closely allied to the condition in Spirorbis. 

 Those from Plymouth may be taken as the type, the fir^t 

 pair of bristh-tufts being conspicuous organs directed 

 forward, u[)ward, and outward. The shaft of eacli bristle is 

 nearly cylindrical, diminishing a little when viewed from 

 behind toward the commencement of the wing, and the 

 tapciing axis can be followed as distinct from the wing to 

 the hair-like tip. The broad basal part of the wing luis 

 numerous (about a dozen) serrations, sloping from the base to 

 the di>tal end in lateral view, then a hiatus occurs, followed 

 by a minutely serrated tapering wing or blade. Certain 

 views i)oint to the double nature of the basal expansion of 

 the «ing. In some from St. Andrews several of the bristles 

 of this tuft do not show the gap separating the more boldly 

 serrated base from the minutely serrated terminal region of 

 the wing. Moreover, a few simple tapering bristles without 

 an evident wing were present. How far these may consist 

 of developing forms has yet to be ascertained, but such is 

 unlikely. These bristles are freely moved forward, outward, 

 and inward for various purposes, and when feeble or dying 

 they stand stiffly forward and outward. In the buds these 

 bri.->tles show the same structure, and slight hollows at the 

 site of the gip between the basal and distal parts of the wing 

 indicate the notch. 



