706 



Eroctfurg of 



brilliant colours. At the base of each series 

 is a fleshy filament, one of which is pro- 

 longed and dilated at its extremity into a 

 flat disc, which fits to the mouth of the shell, 

 and serves to close it when the animal is 

 withdrawn into the tube. These groups are 

 found in tropical regions, where they usually 

 form their habitations in the midst of corals, 

 and lengthen their tubes as the coral is built 

 up around them. Numerous smaller species 

 are also found on our own coasts, some of 

 which are remarkable for the brilliant hues 

 of their expanded gills. Others there are 

 which do not form their tubes by a calca- 

 reous exudation from their own bodies, but 

 by cementing together particles of shell, 

 sand, &c., by means of a glutinous secretion. 



TUBIFERA. The name given by La- 

 marck to an order of the class Polypi, com- 

 prising those which are united upon a com- 

 mon substance fixed at its base, and whose 

 surface is wholly or partially covered with 

 retractile hollow tubes. 



TUBULARIA. The name of a genus of 

 Corallines which have tubes of a horny sub- 

 stance, simple or branched, from the ex- 

 tremities of which the polypes are protruded. 

 Many of them are found in stagnant fresh 

 water ; but the Tubularia marina have two 

 ranges of tentacula, the exterior as rays, the 

 interior as a tuft. 



TTJBULIBRANCHIATA. An order of 

 hermaphrodite Gasteropodous Molluscs, com- 

 prehending those which have the shell in the 

 form of a more or less irregular tube in 

 which the branchiae are lodged. 



TUCUTUCO. (Ctenomys Braziliensis.~) A 

 curious small animal, native of South Ame- 

 rica, described by Mr. Darwin as a rodent, 

 with the habits of a mole. It is extremely 

 abundant in some parts of the country, but 

 is difficult to be procured, and still more 

 difficult to be seen when at liberty. It lives 

 almost entirely under ground, and prefers a 

 sandy soil with a gentle inclination. The 

 burrows are said not to be deep, but of great 

 length. They are nocturnal in their habits; 

 and their principal food is afforded by the 

 roots of plants, which is the object of their 

 extensive and superficial burrows. This 

 animal is universally known by a very pecu- 

 liar noise, which it makes when beneath the 

 ground. A person, the first time he hears 

 it, is much surprised ; for it is not easy to 

 tell whence it comes, nor is it possible to 

 guess what, kind of creature utters it. The 

 noise consists of a short, but not rough, nasal 

 grunt, which is repeated about four times in 

 quick succession ; the first grunt is not so 

 loud, but a little longer, and more distinct 

 than the three following : the musical time 

 of the whole is constant, as often as it is 

 uttered. The name Tucutuco is given in 

 imitation of the sound. In all times of the 

 day, where this animal is abundant, the 

 noise may be heard, and sometimes directly 

 beneath one's feet. When kept in a room 

 the Tucutncos move about slowly and clum- 

 sily, which appears owing to the outward 

 action of their hind legs ; and they are like- 



wise quite incapable of jumping the smallest 

 vertical height, which is accounted for by 

 the socket of the thigh-bone not being at- 

 tached by a ligamentum teres. When eating, 

 they rest on their hind legs and hold the 

 piece in their fore paws Mr. Darwin ob- 

 serves, that the wide plains north of the Rio 

 Colorado are undermined by these animals ; 

 and near the Strait of Magellan, where Pa- 

 tagonia blends with Terra del Fuego, the 

 whole sandy country forms a great warren 

 for the Tucutuco. 



TUI. The native name of a Passerine 

 bird of New Zealand ; it is called by some 

 the "Parson Bird," and by others the 

 "Mocking Bird." It is the Prosthemadera 

 (rnerops} cincinnata [which see]. 



TUNICATA. An order of Acephalous 

 Mollusca; for a lucid and interesting de- 

 scription of which, we are indebted to the 

 ' History of British Mollusca and their Shells, 

 by Prof. E. Forbes, F.R.S., and Sylv. Han- 

 ley, F. L. S.' " The Tunicata are Mollusca 

 which have no true shell, but are enveloped 

 in a coriaceous tunic or mantle ; whence 

 their name. This is constructed in the form 

 of a sac with two openings, or else is shaped 

 like a tube, of greater or less dimensions 

 open at both ends. Within the tunic we 

 find the viscera, consisting of well-defined 

 organs of respiration, circulation, and diges- 

 tion, and a muscular and a nervous system. 

 The branchial organ is usually in the form 

 of a sac, placed at the commencement of the 

 alimentary canal, of which it forms, as it 

 were, the antechamber, and is never arranged 

 in distinct leaflets, as it is in the lamelli- 

 branchiate conchifera. The circulation of 

 their blood is remarkable, on account of its 

 fluctuations and periodical changes of direc- 

 tion. They have no distinct head, and no 

 organs serving as arms or feet. Sometimes 

 they are free, more usually fixed ; but in all 

 cases free during some portion of their exist- 

 ence. Some are simple, some present various 

 degrees of combination ; some are simple in 

 one generation, combined in another. They 

 are all dwellers in the sea. Their various 

 states and structures enable naturalists to 

 group them under several well-marked 

 tribes, of most of which we have examples 

 in the British seas. The best classification 

 of them is that proposed by Professor Milne 

 Edwards. He divides them into three sub- 

 orders, of which the Salpa, the Ascidia, and 

 the Pyrpspma are the types, and subdivides 

 the Ascidians proper into simple, social, and 

 compound. Of all, except the Pyrosoma, 

 we have British examples. 



"These animals attracted the notice of 

 the all-observing Aristotle. Like most phi- 

 losophic naturalists, the question of the dis- 

 tinction between the animal and vegetable 

 kingdoms had for him great attractions. 

 The Ascidia was one of the many creatures 

 which he examined, in the hopes of gaining 

 definite information respecting such distinc- 

 tion. Its inert and sponge-like form, rooted 

 to the ground, seemed to indicate a vegetable 

 nature ; but Aristotle was not content with 

 a mere external survey he explored its 

 internal structure, and soon perceived its 



