184 SPIOPHANES BOMBYX. 



bristles are very long and slender, with hair-like tips, and no wings are visible. They 

 spring from an anterior conical setigerous process also carried inward on the dorsum. 

 The ventral bristles of this foot (Plate CV, figs. 9 and 9 a) are shorter, but similarly 

 filiform at the tip. In addition there are two much thicker curved bristles with a double 

 outline near the tip, and which resemble modified hooks. They are slightly narrowed at 

 the base (Plate CVII, fig. 16), have nearly cylindrical shafts, then diminish toward the 

 hooked tips, which are strongly curved at a little more than a right angle, and end in a 

 sharp point. The double outline passes downward to the curve. These hook-like bristles 

 evidently perform a special function in its tubicular habits, just as the homologous organs 

 of SderocheiliM 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 St. Andrews species has the tip specially differentiated, 

 but there is no wing, though the double outline of the wall of the hook simulates it. 



The ventral lamella of the first foot is lanceolate in outline, broader than the dorsal 

 cirrus and less elongated. It ends in a somewhat pointed tip. 



The dorsal lamella of the second foot is similar in structure and position to the 

 foregoing, and the bristles are equally long and slender. The ventral lamella forms a 

 shorter conical process, and the bristles though shorter are stronger and have a definite 

 curve backward. Traces of wings also occur. 



The dorsal lamella moves gradually to the dorso-lateral region, and the foot at the 

 sixth bristled segment presents a massive lateral enlargement. This is more clearly shown 

 at the tenth foot (Plate XCVII, fig. 6). The dorsal lamella is now considerably shorter, 

 though still subulate, the base is broad, and the bristles can be differentiated into a 

 longer upper series and. a shorter and stouter inferior 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 dorsal 

 lamella, and contains a cellular structure like a cyst. The ventral bristles are short and 

 stout, the lower forms conspicuously curved backward at the tip, which is minutely dotted 

 or mottled as well as winged (Plate CVI, fig. 9), and is indeed the special bristle figured 

 by Mesnil, so different 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 fourth 

 to the fourteenth. In its progress backward the dorsal lamella or cirrus becomes less, and 

 presents a ventral enlargement, which is very marked, for instance, at the fifteenth foot 

 (Plate XCVII, fig. 6 a), the massive base being in contact 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 

 pointing downward. 



The foot considerably diminishes from the twentieth to the thirtieth. Thus at the 

 twenty-fifth (Plate XCVII, fig. 6 b) the form of the dorsal cirrus or lamella is charac- 

 teristic, its base having the shape of a leg of mutton, with the shank formed by the tapering 

 cirrus. The dorsal bristles are still arranged in a fan-like tuft, the upper being the longer, 

 and a line of powerful cilia runs inward from the foot on the dorsum. The region between 

 the divisions is much reduced, and below the hook two of the powerful bristles with the 

 dotted distal regions occur. They are slightly curved and taper to a sharp point. The 



