278 NATURAL HISTORY. 



is attached solely by the contractile " rod-like " funiculus. There is no mantle or inner layer of the 

 cell-wall, and the cavity becomes filled with sea-water. No muscles are developed, the animal raising 

 itself in the cell by means of the foot. Protrusion, a slow process, takes several hours to accomplish, 

 and the animal is retracted by the elastic funiculus. The detached bud is furnished with two valve- 

 like fleshy plates. The unique Rhabdopleura has been dredged in the British and northern seas 

 in from ten to three hundred fathoms. Although a marine form, according to its describers, Sars 

 and Allman, it presents many resemblances to the fresh-water genera, and is the representative of 

 a very old type. It is supposed that the Graptolites are allied. 



The Moss-animals sustain life under the most variable conditions of temperature and depth. 

 Some affect shallow, muddy waters, others the regions of clear water or strong currents, and several 

 species exist in the dim and unruffled abysses of the ocean. They are numerously represented in 

 temperate regions, in the frozen waters of the east Greenland coast (Kirchenpauer), and in the 

 warm latitudes of the Australian shores. They encrust the floating Gulf-weed with their silvery 

 network, and grow on reefs between and on the different clumps of coral. Many species are universally 

 distributed, others characterise boreal regions or the tropical zones. One, at least, leads a roving 

 existence, and attached to the keels of ships is borne from clime to clime. The Cheilostomata and 

 Cyclostomata are specifically most abundant from between tide marks to depths of 200 

 fathoms. They are somewhat less frequently recorded from 200 to 600 fathoms. A few 

 species of the " lip-mouthed " forms frequent the brackish waters of friths and the mouths of 

 tidal rivers, but the deep-sea species appear as usual to be widely diffused. Those dredged by 

 H.M.S. Challenger have been described by Dr. Busk, and the occurrence in the Atlantic of several of 

 the "lip-mouthed " sub-order at depths varying from 1,500 to 3,000 fathoms is noteworthy. Among 

 these abysmal forms was a species of a cosmopolitan genus, with a range from shallow water to 

 great depths, and closely allied to members of a group that existed in Cretaceous oceans. This 

 was brought \ip from between 2,000 and 3,000 fathoms, in a sterile region where other animal life 

 was scarce. A peculiarly interesting and novel species (Kinetoskias cyathus), ai-ising from fibrous 

 roots possessing the long, slender stem of the Endoprocta, supporting branches forming a cup, yet 

 characterised by the colonial growth and appendages of the most highly organised class, was dredged 

 in 1,500 fathoms off the Island of St. Vincent, and elsewhere in 2,650 fathoms. The Ctenostomata 

 and other marine forms apparently prefer depths under a hundred fathoms. Two hundred and thirty 

 species in all occur in the British seas. The fresh-water genera are distributed in the still and 

 running waters of Europe, India, and North America, at depths ranging from a few inches below the 

 surface to four feet.* 



Although the Bryozoa are of comparatively little importance as reef-builders in the present 

 day, in past ages beds of limestone of considerable extent and thickness were built up by their 

 exclusive agency. Fragments of the calcareous or horny skeletons of the "lip-" and "circular- 

 mouthed " species remain when the soft parts decay, and, frequently, preserved in a fossil state, 

 testify that genera closely allied to living species have existed even from early epochs. Excluding 

 a doubtful Cambrian form, we find a large number both of the erect and net-like forms (Retepora, 

 Fenestella), and the delicate encrusting types, in rocks of Lower and Upper Silurian age. Some 

 of these died out, others persisted, and many new forms appeared in the succeeding Devonian and 

 Carboniferous epochs. Closely-related forms occur in the Trias. During the Mesozoic period, the 

 Moss-animals contributed largely to the formation of extensive deposits, and attained their maximum. 

 Jules Haime has described a number of Jurassic species, and D'Orbigny figured eight hundred 

 from the Cretaceous rocks of France alone. Some Palaeozoic and Mesozoic genera (Stomatopora 

 and Diastopora) still continue to be represented ; while the perforating Hippothoa has persisted 

 from the Silurian, but the majority of generic forms are restricted to one life-epoch, and many occur 

 only in a single geological horizon. Bryozoa abounded in the Miocene, and many species from the 

 later Tertiary deposits are stated to be closely allied to, and even identical with, species living 

 in the present oceans. 



* In Vol. xx. of the Challenger Keports (Zoology), Prof. M'lntosh and Mr. S. "VV. Harmer described, from 245 fathoms in 

 the Straits of Magellan, a remarkably abnormal colonial Bryozoon (Cephalodiscus dodecalophus) with a notocLord and a pair 

 of gill slits and allied to Rhabdopleura. 



