COMMEMORATION. 207 COMMENSALISM. the glories of this season have tended more and more to be eclipsed by those of the 'Eights Week,' when the college eight-oared races are rowed, early in ilay. See Oxford University. COMMEMORATION ODE. An ode by James Russell Lowell, read at exercises held at ('anibridge in 18G5, in commemoration of the Harvard men who had served in the Civil War. COMMENCEMENT (OF., Fr. commence- mcHt, from OF. comcncer, Fr. commencer, It. cominciare, to begin, from Lat. con-, together + iniliare, to begin, from initium, beginning, from iiiirc, to enter, from in, in + ire, to go). In American colleges, the name given to the concluding exercises of the college year, when degrees are conferred upon the bachelors, mas- ters, and doctors completing their respective courses of study. The term is applied loosely to the graduating exercises of academies, secondary schools, etc. The custom originated in the me- diipval universities, though the appropriate term was 'inception.' The inception involved two ejemeuts: (1) The recognition of the graduate or new teacher by his old master and other members of the profession; (2) the formal en- trance of the newly licensed teaclicr upon his work by the actual performance of its duties. Hence, an essential feature of the exercises was tliat the recipient of the bachelor's degree should 'incept' or teach, and that the recipients of the liigher degrees should defend a thesis. At Oxford this occasion was called Commemora- tion; but at Cambridge it was, and is yet. called Commencement. The 'inceptor' was there called 'commencer" — that is_. one who commenced to teacli. The ceremony and the term were a part of the inheritance received by Harvard Col- lege from Cambridge University, and thus be- came general among American colleges. This exercise in Colonial days was held in the fall, at the commencement of the college year, and the term is often, though erroneously, supposed to refer to tliis fact. As the mediieval bachelor 'incepted,' or taught, the graduate of the Ameri- can college delivered an oration or dissertation before receiving his degree. With the larger colleges, even this moditication of the old custom is now commonly abandoned, and in many places the Commencement exercises include only the address by the president or some distinguished educator, and the conferring of degrees. See University; Degree: College; Curriculum. COMMEN'DAM (JIL., ace. sg. of commenda, trust, from Lat. coininendare, to intrust, from com-, together -j- mandare, to intrust, from manus, hand -^- dare, to give; originally used in the ))hrases in commendam dare, to give in trust, or in commendam mittere, to send in trust). A term in ecclesiastical law to denote a benetice which, being void, is commended to the care of some sufTicient clerk to be supplied until it may be conveniently provided with a pastor. In former times bishops frequently held livings in com- mendam, in order to appropriate the revenues. The practice has well-nigli ceased in Europe, and does not exist in the United States. In the Church of England, commendams were abolished in 18.30. See Abbot. COMMENDATION (Lat. commendatio, from eommendnre. to intrust). In feudal customs, the act by which a free man became a vassal. See Feudalism. COMMENDATION OF OUR LADY, Bai,- L.UE IX. A l)aUad improperly attributed to Chaucer, according to Tyrwhitt ; but really the same poem as the Invocation of Our Lady, ascribed to Lydgatc. COMMENSALISM (ML. commen.iali.'!, eat- ing at the same table, from Lat. com-, together -f- mensa, table). A sort of partnership or asso- ciation of two different kinds of organisms by which they endure each other's presence, do each other no harm, and in many cases are of mutual advantage; such are said to be commensals or messmates. This occurs chiefly among marine invertebrates, and is ditl'erent from parasitism. ilany commensals are quite free to separate, yet never dwell apart, and often could not main- tain a separate existence. Others grow together so completely that they cannot sejjarate if they would, yet are not parasites, because each re- tains its form and faculties, while a true para- site changes these in such a manner that it is no longer capable of obtaining food luitil it has been elaborated for it b}' the functions of its host. The most familiar example of connnen- salism is the small crab so often met with inside the shells of oysters — the pinnothere, or oyster- crab. Similar crabs inhabit various bivalves the world over, to the mutual satisfaction of guest and host. Within the shelter of the mollusk's pearly house the little crab is safe from its enemies, yet can dash out whenever it observes any prey in the offing and bring it home to be devoured ; and the crumbs may be welcome to the oyster. The most striking examples, jjer- haps, are found among cojlenterates and crus- taceans. In the midst of the trailing tentacles, covered with stinging cells, of the Portuguese man-of-war and several jelly-fishes, live small fishes, comparatively safe from pursuit of their fees; small fishes also seek refuge among the tentacles of sea-anemones and within holothu- rians. ilollusks live in the burrows of sea- urchins that move about in the sand, and in the holes made by the erustaceous Gebia — a reversal of the oyster and cr,ab. Certain Dromia crabs carry sponges, ascidians, or sea-anemones on their backs or claws. The anemones serve to conceal, and, by means of their nettling organs, protect the crab, while they get fragments of the crab's food, or, by being transported from place to place, come in contact with more food tlian if they were stationary. One hermit-crab (q.v. ) always bears an anemone upon its claw, which is so placed that it blocks the entrance to the shell when the erab retreats within. If the anemone dies or is removed, the erab is at pains to find and transfer a new anemone to its claw. A still more curious case is that of a polyp (Oem- rnnria Americana), found in deep water off the Newfoundland coast and allied to the sea- anemones, which attaches itself to the .shell of a kind of hermit-crab, and by budding gradu- ally covers the entire Shell with a colony. "It possesses the power of dissolving the shell so that no trace of it can be found. As the polyp colony increases in size as fast as the crab grows, there is no need for the latter to change its abode, while its neighbors and competitors must frequently expose themselves to the dis- comforts and dangers of house-hunting." Consult: Van Veneden. Animal Parasifes and Mesxmates (New York, 1876) ; Cambridge Natural History,
