LAMP-SHELLS — SEA- MA TS — SEA- WORMS 385 



Another genus, with numerous species, is the sharp-beaked Rhynchonella, in which 

 the shell is ribbed instead of smooth. These two genera are nearly related, but an 

 altogether different type is presented by the horny-shelled Lingula anatina, 

 of the Indo- Pacific, which is much larger, and nearly flat, with a long stalk ; the 

 colour of the shell being pale green with a banded arrangement. The special interest 

 of the lingula lies in the fact that it represents one of the most ancient generic 

 types in existence ; the genus dating, in fact, from the lower part of the Palaeozoic 

 epoch, that is to say, from a period (the Cambrian) long antecedent to that 

 during which our coalfields were laid down. These brachiopods live in tubes in the 

 sand in shallow water, the shell occupying the upper portion of the tube, with its 

 aperture just below the surface, while the stalk, which may be six inches in length, 

 fills the lower cylindrical portion ; this lower portion being lined with mucus. 

 When frightened, the stalk is contracted and the shell suddenly withdrawn half- 

 way down the tube. 



A few lines must suffice for the so-called sea-mats, which are 

 Sea-Mats. . 



commonly mistaken tor sea-weeds, although they are really colonies 



of polyps of a comparatively high grade of organisation and related to the 



brachiopods, but representing a distinct class, the Polyzoa or Bryozoa. One 



of the well-known species is the broad-leaved horn-wrack, or sea-mat (Flustra 



foliacea), which is to be found among the heaps of sea-weed cast up by the tide. On 



examination with a lens, it will be seen that the surface of the mat is divided into 



a number of small cells, each of which, during life, contains a polyp ; these polyps, 



when active, protruding a delicate plume of tentacles. When inactive, each cell in 



this particular genus, although not in others, is closed by a lid. The organism 



is attached by a stalk to a stone or other object. 



__ Among the countless hosts of marine worms, or annelids, attention 



Sea- Worms. ° . 



must be mainly restricted to the curious palolo worm of Samoa and 



Fiji. For more than half a century the appearance of swarms of these worms in 



the sea, apparently always just before the full moon, in October and November, 



has been familiar, and it has also been known that the worms forming these 



swarms are always imperfect. It is now ascertained that these palolo are the 



slender posterior generative portion of the annelid known as Eunice viridis,. 



which at the swarming season becomes detached and free-swimming. This portion 



is very much longer than the proper body of the creature, which is, however, 



much stouter. The complete worm dwells in coral-reefs, into which it burrows ~ r 



and, curiously enough, its existence there was quite unknown to the Samoans, to- 



whom the demonstration of its presence by an American naturalist came as a. 



revelation. The worm only attains its full dimensions shortly before the swarming 



season. Another worm (Ceratocejihale osawai) at certain seasons appears in swarms 



in the Gulf of Tokyo and the rivers debouching therein, after the manner of the 



palolo. Instead, however, of belonging to the Eunicidce, the Japanese species 



is referable to the Lycoridce. According to the experience of the fishermen, the 



Japanese ' palolo ' swarms during the months of October and November, usually 



in four periods of a few days' duration each. The swarming season always takes 



place when the moon is either new or near the full, and invariably occurs in the 



evening just after flood-tide. On one occasion, the height of the swarm did not 



vol. in. — 25 



