POLYDOEA CILIATA. 203 



are shorter than the rest, and those in the neighbourhood of the sucker are longer and 

 more slender in proportion to the breadth of the region. 



The terminal sucker (Plate XCVIII, fig. 15) forms a beautiful cup^shaped organ 

 with a dorsal median notch, and a crenation on each side, the rim then curving gently 

 outward to join the general level of the cup. During the various movements of the 

 animal, the notch and the crenations at its side change their appearances, as shown in the 

 several figures. 



The winged hooks (Plate CVI, fig. 2 d) dilate a little from the base upward to the 

 bold forward curve, then diminish slightly to the neck from which the main fang comes 

 off at more than a right angle. The single spur on the crown is very slightly oblique, 

 that is, nearly approaches the vertical. The wing passes a considerable distance down the 

 neck, touches the tip of the spur on the crown, and forms a border posteriorly. It is 

 perhaps a little shorter in the posterior hooks. 



This species also bores in masses of water-logged softened wood, its tubes, about half 

 an inch in length, covering the surface. 



Post-larval stages, from tow-nets, are shown in Plate XCIII, figs. 6 and 7. 

 Larval PolydoraB make their appearance in the bottom tow-net at the beginning of 

 July, and at the surface about the end of that month. 



Reproduction. — Numerous ova occurred in the vessels in which ruptured examples 

 were on January 23rd. They are opaque, granular, and somewhat ovoid, and do not 

 show a reticulated capsule, but they are probably immature. 



At Naples, Lo Bianco (1909) states that sexual maturity occurs from October to May. 

 The pelagic larvae are found in February. 



What the Polydora cornuta of Bosc and others may be is open to doubt. It may be 

 Polydora ciliala, though Claparede 1 appeared to think it different from any known form. 

 Frey and Leuckart (1847) describe under the name of larva of Leucodorum ciliatum 

 a Spionid larva in the beginning of July with ten pairs of bristle tufts, the first very long. 

 No sign of the hooks of the fifth segment is seen. The head bears six small eye-specks 

 and two large lateral eyes. A caudal ring of cilia. A muscular pharynx and alimentary 

 canal are outlined. 



Claparede (1863) described the development of a form he considered to be Polydora 

 ciliata at St. Vaast-la-Hougue. The youngest stage is a rounded trochophore with 

 numerous yolk-granules internally and a ciliated anterior region. In the next stage a 

 tuft of long, jointed provisional bristles occurs at each side behind the projecting shelf 

 or swimming ring with its cilia, and the ventral " bite " for the mouth. Two eyes 

 anteriorly, and two pigment-cells posteriorly, characterise the larva, wdiich has the aspect 

 of two blunt cones joined by their bases. Then a fold or collar develops in front of 

 the swimming ring, with a central and slightly bifid median projection, and five bristled 

 segments, all with the articulated bristles, appear, the first having the longest bristles, 

 the others regularly diminishing. A telotroch is present, and the naked region in front 

 of it has a ciliated band where it joins the preceding segment. The alimentary canal 

 is formed, and the four posterior bristled segments have each a conspicuous stellate 

 pigment-spot. Amongst changes which ensue between this and a later stage with 



1 ( Recherches Anat./ p. 47, 1864. 



