Page:EB1911 - Volume 18.djvu/207

 ova which are free, in the cylindrical forms; they leave the mother through the dehiscing of the cells of the non-ciliated ring, are fertilized and develop parthenogenetically into females both flat and cylindrical.

R. pelseneeri and S. giardi are said to be hermaphrodite. The parasites first make their appearance in a host in the form of a plasmodium comparable with the sporocyst of a Trematode. By the segregation of nuclei and some of the surrounding protoplasm, germ cells arise which develop into ciliated larvae and ultimately into males and females which only discharge their spermatozoa and ova when they reach sea-water. The product of the consequent fertilization is unknown; presumably it infects new hosts, entering them in the form of a nucleated plasmodium.

The original idea that in the Rhombozoa and Orthonectida we had animals intermediate between the Protozoa and Metazoa is no longer widely held. The modern view is that the simplicity of their structure is secondary and not primary, and is correlated with their parasitic habit of life. They are probably derived from some Platyhelminthine ancestor and perhaps come nearer to the Trematoda than to any other group.

—E. van Beneden, ''Bull. Ac. Belgique'' (2), (1876) xli. 85, 116; (1876), xlii. 35; also ''Arch. Biol.'' (1882), iii. 197; C. O. Whitman, ''Mt. Stat. Neapel.'' (1883), iv. 1; W. M. Wheeler, Zool. Anz., (1899), xxii. 169; A. Giard, ''Jour. anat. physiol.'' (1879), xv. 449; ''Quart. Jour. Micr. Sci.'' (1880), xx. 225; St Joseph, ''Bull. Soc.'' ''Zool. France'' (1896), xxi. 58; Caullery and Mesnil, ''C. R. ac. sci.'' (1899), cxxviii. 457 and 516; C. Julin, ''Arch. Biol.'' (1882), iii. 1; E. Nerescheimer, ''Zeitschr. wiss. Zool.'' (1904), lxxvi. 137; V. A. Dogiel, ''Trav. soc. imp. natur. St Pètersbourg'' (1907), xxxviii. 28, and ''Zool. Anz.'' (1906), xxx. 895.

 MESOZOIC ERA, in geology, the name given to the period of time between the Palaeozoic and Cainozoic eras; it is synonymous with the older and less satisfactory term “Secondary” as applied to the major divisions of geological time and with the “Flözgebirge” of the Wernerian school. This era is subdivided into a lower, Triassic, a middle, Jurassic, and an upper, Cretaceous period or epoch. The duration of the Mesozoic era was not more than one fourth of that of the Palaeozoic era, measured by the thickness of strata formed during these periods. It was an era marked by peaceful conditions in the earth’s crust and by a general freedom from volcanic activity. The sediments as a whole are characterized by the prevalence of limestones as compared with those of the preceding era; they are seldom much altered or disturbed except in the younger mountain regions. Mammals, represented by small marsupials, and primitive forms of birds and bony fishes make their first appearance in rocks of Mesozoic age. Saurian reptiles played an extremely prominent part; ammonites and belemnites lived in extraordinary variety in the seas along with the echinoids and pelecypods, which had to a great extent supplanted the crinoids and brachiopods of the preceding periods. The first clear indications of monocotyledonous and dicotyledonous angiosperms made their appearance, while Cycads and Conifers constituted the bulk of the land flora.  MESQUITE, or, in botany, a tree, native of the southern United States and extending southwards through Mexico and the Andean region to Chile and the Argentine Republic. It is known botanically as Prosopis juliflora, and belongs to the natural order Leguminosae (suborder Mimoseae). It reaches 40 or 50 ft. in height with a trunk usually not more than 6 to 12 in. in diameter, and divided a short distance above the ground into numerous irregular crooked branches forming a loose straggling head. The remarkable development of its main root in relation to water-supply renders it most valuable as a dry-country plant; the root descends to a great depth in search of water, and does not branch or decrease much in diameter till this is reached. It can thus flourish where no other woody plant can exist, and its presence and condition afford almost certain indications of the depth of the water-level. When the plant attains the size of a tree, water will be found within 40 or 50 ft. of the surface; when it grows as a bush, between 50 or 60 ft.; while, when the roots have to descend below 60 ft., the stems are only 2 or 3 ft. high. These woody roots supply valuable fuel in regions where no wood of fuel value is produced above ground. The leaves are compound, the main axis bearing two or sometimes four secondary axes on which are borne a number of pairs of narrow bluntish leaflets. The minute greenish-white fragrant flowers are densely crowded

on slender cylindrical spikes from 1 to 4 in. long; the long narrow pods are constricted between the seeds, of which they contain from ten to thirty surrounded by a thick spongy layer of sweet pulp. The wood is heavy, hard and close-grained but not very strong; it is almost indestructible in contact with soil, and is largely used for fence-posts and railway ties. The ripe pods supply the Mexicans and Indians with a nutritious food; and a gum resembling gum arabic exudes from the stem.

An allied species Prosopis pubescens, a small tree or tall shrub, native of the arid regions of the south-western United States, is known as the screw-bean or screw-pod mesquite from the fact that the pods are twisted into a dense screw-like spiral; they are used for fodder and are sweet and nutritious, but smaller and less valuable than those of the mesquite.

 MESS (an adaptation of O. Fr. mes, mod. mets; Ital. messo; derived from the Late Lat. missum, past participle of mittere “to send or place in position”), a service of meat, a dish sent to table. The term is also used of the persons who are in the habit of eating their meals together, and thus particularly of the parties into which a ship’s company or a regiment is divided, either according to their rank, or for convenience in catering. Originally, a mess in this sense was a group of four persons sitting at one table and helped from the same dishes. In the Inns of Court, London, the original number is preserved, four benchers or four students dining together.

 MESSAGE (a word occurring in slightly different forms in several languages, e.g. Fr. message, Span. mensaje, Ital. messagio; adapted from the Low Lat. missaticum, from mittere), a communication either verbal, written or printed, sent from one person to another. Message is the term generally applied to the official communications addressed by the heads of states to their legislatures at the opening of the session or at other times. These also, though written, are borne and delivered by special messengers and have the force of a face to face speech. The sessional and other messages to Congress of the president of the United States of America are printed state documents. Washington and John Adams delivered them in person but the practice was discontinued by Jefferson.

“Messenger” is of the same derivation; the earlier form of the word was messager (cf. passenger, scavenger). In ordinary language the word means one who is charged with the delivery of a message. In Scottish law a messenger-at-arms is an official appointed by Lyon-King-at-Arms to execute summonses and letters of diligence connected with the Court of Sessions and Court of Justiciary (see : § Scotland). Technically the term “messenger” is given to an endless rope or chain, passing from the capstan to the cable so that the latter may be hauled in when the messenger is wound round the capstan; also to a similar contrivance for hauling in a dredge.  MESSAGER, ANDRE CHARLES PROSPER (1853–), French musician, was born at Montluçon on the 30th of December 1853; he studied at Paris, and in 1874 became organist at St Sulpice. He was for some time a pupil of Saint-Saëns. In 1876 he won the gold medal of the Société des Compositeurs with a symphony. In 1880 he was appointed music director at Ste Marie-des-Batignolles. In 1883 he completed Firmin Bernicat’s comic opera François des bas bleus; and in 1885 produced his own operettas, La Fauvette du temple and La Béarnaise, the latter being performed in London in 1886. His ballet Les Deux pigeons was produced at the Paris Opéra in 1886. But it was the production of his comic opera La Basoche in 1890 at the Opéra Comique (English version in London the following year) that established his reputation; and subsequently this was increased by such tuneful and tasteful light