392 POLYXOE SCOLOPENDRINA. 



Digestive System. — The pre-gastric caeca are two in number, both being short and 

 broadly club-shaped. The third is transverse. All go deeply into the intermuscular 

 spaces at the feet. The movements of muscles and feet must thus have considerable 

 effect on the contents of the caeca. 



Scales (Plate XXXIII, figs. 13 — small example, and 14 — larger example) fifteen 

 pairs. They vary in appearance according to the condition of the specimen; thus the 

 smaller race from the Channel Islands has the anterior scales dappled brownish with a 

 dark patch over the scar for attachment, and surrounded by a broad pale ring. In the 

 larger specimens from the Hebrides they have a dark metallic (steel-like) iridescence. 

 When removed they are translucent, pale anteriorly, marked by a dark belt, speckled 

 with translucent spots round the inner three-fourths of their circumference, and with a 

 pale centre. They vary, in any given specimen, in size according to state of development, 

 covering the dorsum in some nearly as far as they extend, whereas in others with 

 developing scales an interval occurs between the pairs. In the large forms the first five 

 pairs cover the dorsum completely, the rest leave a space in the centre. The first pair 

 are rounded — with minute cilia anteriorly, the succeeding somewhat reniform, and the rest 

 more or less rounded ovoid. Though smooth under a lens they have a dense series of 

 minute papillae as a broad belt along the anterior region, and at the outer border a series 

 of minute papillae or cilia, and one or two also occur along the posterior border. Finely 

 branched nerves ramify throughout the scale from the scar for the pedicle. In the small 

 specimens from the Channel Islands the papillae (spines) on the scales are proportionally 

 large, as observed in the sketch. 



Feet. — The dorsal division of the first foot presents a single small dorsal bristle with 

 about seven or eight spinous rows, and a smooth tip. 



The second foot has dorsally a group of somewhat tapered, short, slightly curved 

 bristles with well-marked spinous rows. Ventrally the slender bristles are also short, 

 the spinous regions being bent dorsally, and tapering to smooth bifid tips. The rows of 

 spines are well marked, — that is, are at moderate distances from each other. The tips of 

 one or two of the inferior bristles are simple. The large ventral cirrus of this foot has 

 numerous cilia with clavate and truncate tips. The bristles in the succeeding feet gradu- 

 ally approach the typical form, which is found about the twelfth or thirteenth bristled 

 foot. In shape the typical foot (Plate XXIX, fig. 17) presents dorsally the comparatively 

 short tapering cirrus, then the eminence for the dorsal bristles. The inferior division is 

 bifid, with a long anterior process and a shorter posterior cushion, the margin beneath 

 having an inward slope from above downward. Even in the second foot the upper 

 ventral bristle is stouter than the others, with strongly bifid tip and spinous rows. It 

 increases in strength and becomes more boldly bifid as we proceed backward, attaining a 

 large size in the fifth and sixth, and then becoming simple about the tenth bristled foot, 

 while only traces of the spines remain. As a rule only one strong bristle occurs in the 

 typical foot, which has below the dorsal cirrus thQ tuft of short, slightly curved, and little 

 tapered dorsal bristles arising from a small eminence (Plate XLI, fig. 4). These bristles 

 taper a little from the base, but end in a blunt tip (Plate XLI, fig. 7), which is curiously 

 wrinkled so as to appear bifid. The spinous rows are somewhat close, yet fairly distinct. 

 A careful examination of various specimens, however, shows that this condition of the 



