Page:EB1911 - Volume 13.djvu/366

 characteristic scene in man’s long history. The verse is flawless, polished like a gem; and its sound has distinction and fine harmony. If one may suggest a fault, it is that each picture is sometimes too much of a picture only, and that the poetical line, like that of M. de Heredia’s master, Leconte de Lisle himself, is occasionally overcrowded. M. de Heredia was none the less one of the most skilful craftsmen who ever practised the art of verse. In 1901 he became librarian of the Bibliothèque de l’Arsénal at Paris. He died at the Château de Bourdonné (Seine-et-Oise) on the 3rd of October 1905, having completed his critical edition of André Chénier’s works.

 HEREDIA Y CAMPUZANO, JOSÉ MARIA (1803–1839), Cuban poet, was born at Santiago de Cuba on the 31st of December 1803, studied at the university of Havana, and was called to the bar in 1823. In the autumn of 1823 he was arrested on a charge of conspiracy against the Spanish government, and was sentenced to banishment for life. He took refuge in the United States, published a volume of verses at New York in 1825, and then went to Mexico, where, becoming naturalized, he obtained a post as magistrate. In 1832 a collection of his poems was issued at Toluca, and in 1836 he obtained permission to visit Cuba for two months. Disappointed in his political ambitions, and broken in health, Heredia returned to Mexico in January 1837, and died at Toluca on the 21st of May 1839. Many of his earlier pieces are merely clever translations from French, English and Italian; but his originality is placed beyond doubt by such poems as the Himno del desterrado, the epistle to Emilia, Desengaños, and the celebrated ode to Niagara. Bello may be thought to excel Heredia in execution, and a few lines of Olmedo’s Canto á Junín vibrate with a virile passion to which the Cuban poet rarely attained; but the sincerity of his patriotism and the sublimity of his imagination have secured for Heredia a real supremacy among Spanish-American poets.

 HEREDITAMENT (from Lat. hereditare, to inherit, heres, heir), in law, every kind of property that can be inherited. Hereditaments are divided into corporeal and incorporeal; corporeal hereditaments are “such as affect the senses, and may be seen and handled by the body; incorporeal are not the subject of sensation, can neither be seen nor handled, are creatures of the mind, and exist only in contemplation” (Blackstone, Commentaries). An example of a corporeal hereditament is land held in freehold, of incorporeal hereditaments, tithes, advowsons, pensions, annuities, rents, franchises, &c. It is still used in the phrase “lands, tenements and hereditaments” to describe property in land, as distinguished from goods and chattels or movable property.

 HEREDITY, in biological science, the name given to the generalization, drawn from the observed facts, that animals and plants closely resemble their progenitors. (That the resemblance is not complete involves in the first place the subject of variation (see ); but it must be clearly stated that there is no adequate ground for the current loose statements as to the existence of opposing “laws” or “forces” of heredity and variation.) In the simplest cases there seems to be no separate problem of heredity. When a creeping plant propagates itself by runners, when a Nais or Myrianida breaks up into a series of similar segments, each of which becomes a worm like the parent, we have to do with the general fact that growing organisms tend to display a symmetrical repetition of equivalent parts, and that reproduction by fission is simply a special case of metamerism. When we try to answer the question why the segments of an organism resemble one another, whether they remain in association to form a segmented animal, or break into different animals, we come to the conclusion, which at least is on the way to an answer, that it is because they are formed from pieces of the same protoplasm, growing under similar conditions. It is apparently a fundamental property of protoplasm to be able to multiply by division into parts, the properties of which are similar to each other and to those of the parent.

This leads us directly to the cases of reproduction where there is an obvious problem of heredity. In the majority of cases among animals and plants the new organisms arise from portions of living matter, separated from the parents, but different from the parents in size and structure. These germs of the new organisms may be spores, reproductive cells, fused reproductive cells or multicellular masses (see ). For the present purpose it is enough to state that they consist of portions of the parental protoplasm. These pass through an embryological history, in which by growth, multiplication and specialization they form structures closely resembling the parents. Now, if it could be shown that these reproductive masses arose directly from the reproductive masses which formed the parent body, the problems of heredity would be extremely simplified. If the first division of a reproductive cell set apart one mass to lie dormant for a time and ultimately to form the reproductive cells of the new generation, while the other mass, exactly of the same kind, developed directly into the new organism, then heredity would simply be a delayed case of what is called organic symmetry, the tendency of similar living material to develop in similar ways under the stimulus of similar external conditions. The cases in which this happens are very rare. In the Diptera the first division of the egg-cell separates the nuclear material of the subsequent reproductive cells from the material that is elaborated into the new organism to contain these cells. In the Daphnidae and in Sagitta a similar separation occurs at slightly later stages; in vertebrates it occurs much later; while in some hydroids the germ-cells do not arise in the individual which is developed from the egg-cell at all, but in a much later generation, which is produced from the first by budding. However, it is not necessary to dismiss the fertile idea of what Moritz Nussbaum and August Weismann, who drew attention to it, called “continuity of the germ-plasm.” Weismann has shown that an actual series of organic forms might be drawn up in which the formation of germ-cells begins at stages successively more remote from the first division of the egg-cell. He has also shown evidence, singularly complete in the case of the hydroids, for the existence of an actual migration of the place of formation of the germ-cells, the migration reaching farther and farther from the egg-cell. He has elaborated the conception of the germ-track, a chain of cell generations in the development of any creature along which the reproductive material saved over from the development of one generation for the germ-cells of the next generation is handed on in a latent condition to its ultimate position. And thus he supposes a real continuity of the germ-plasm, extending from generation to generation in spite of the apparent discontinuity in the observed cases. The conception certainly ranks among the most luminous and most fertile contributions of the 19th century to biological thought, and it is necessary to examine at greater length the superstructure which Weismann has raised upon it.

Weismann’s Theory of the Germ-plasm.—A living being takes its individual origin only where there is separated from the stock of the parent a little piece of the peculiar reproductive plasm, the so-called germ-plasm. In sexless reproduction one parent is enough; in sexual reproduction equivalent masses of germ-plasm from each parent combine to form the new individual. The germ-plasm resides in the nucleus of cells, and Weismann identifies it with the nuclear material named chromatin. Like ordinary protoplasm, of which the bulk of cell bodies is composed, germ-plasm is a living material, capable of growing in bulk without alteration of structure when it is supplied with appropriate food. But it is a living material much more complex than protoplasm. In the first place, the mass of germ-plasm which is the starting-point of a new individual consists of several, sometimes of many, pieces named “idants,” which are either the chromosomes into a definite number of which the nuclear material of a dividing cell breaks up, or possibly smaller units named chromomeres. These idants are a collection of “ids,” which Weismann tentatively identifies with the microsomata contained in the chromosomes, which are visible after treatment with certain reagents. Each id contains all the 