163 Prof. M'Intosli's Notes from the 



but similarly filiform at the tip. In addition two much 

 thicker bristles, winged at the tip^ resemble modified hooks, 

 since they end in a small claw-like tip. These hook-like 

 bristles apparently perform a special function in the tubi- 

 colous habits of the species, just as the homologous organs 

 of Scleroclieilus do. Either considerable variation occurs or 

 Mesnil's figure of these organs is at fault, for he shows and 

 describes them as having a simple tapering tip and winged 

 in the ordinary way, whereas the specimens from St. Andrews 

 have the tips specially differentiated and the wing adjusted 

 like that of a hook. 



The dorsal lamella moves gradually to the dorso-lateral 

 region, and the foot at the Gth bristled segment presents a 

 massive lateral enlargement. This is more clearly shown at 

 the 10th foot, the dorsal lamella being now considerably 

 shorter, though still subulate, and the base is broad. The 

 dorsal bristles can be differentiated into a longer upper series 

 and a shorter and stouter lower series, as usual in the group, 

 and they spread in a fan-like manner in front of the dorsal 

 lamella. The ventral lamella has been modified into a great 

 lateral mass which passes upward to the base of the dorsul 

 lamella. The ventral bristles are short and stout, the lower 

 forms distinctly curved backward at the tip, which is 

 minutely dotted or mottled as well as winged, and appears, 

 indeed, to be the special i)ristle figuied by Mesnil — so diffe- 

 rent from the two peculiar hook-like bristles of the ventral 

 division of the first segment. The laterally enlarged feet 

 seem to be most prominent from the 4th to the 14th. In its 

 progress backward the dorsal lamella or cirrus becomes less 

 and presents a ventral enlargement, which is very marked, 

 fur instance, at the 15th segment, the massive base being in 

 contrast with the slender distal process. Moreover, the 

 winged hooks appear in the ventral division of this foot as a 

 row of four, and beneath them is a single strong curved 

 bristle or two with the dotted or mottled tip, which points 

 downward. The feet considerably diminish from the 20th 

 to the 30th. Thus at the 25tli the shape of the dorsal cirrus 

 or lamella is like that of a leg of mutton, the shank formed 

 by the tapering cirrus it-elf. Tie dorsal bristles are still 

 arranged in a fan-like tuft, the upper being the larger, and a 

 line of powerful cilia runs from the foot inward on the 

 dorsum. The space between the divisions is much reduced, 

 and below the hooks are two of the powerful, slightly curved 

 bristles which have the dotted distal regions and sharp points. 

 The winged hooks are proportionally small, have a slightly 

 curved and sharp main fang, coming off nearly at a light 



