Page:The New International Encyclopædia 1st ed. v. 17.djvu/54

BEPRISAL. 38 at sen or of any property within the jurisdiction of llic State, whether belonging to the State or lo private litizeiis. Bluntschli mentions in addi- tion the following acts of reprisal as permissihlo by the law of nations: interru)ition of means of comniunieation, detention of subjects of the of- fending Stale as hostages, the exi)ulsiou or im- prisonm<>nt of its subjects, refusal to be bound by treaty sti|>ulations or other international agree- ment's, and the withdrawal of privileges and pro- tection to the subjects of the olVending State. See IaKTohsiox. REPKODUCTION (from Lat. re-, back again, anew + produceic, to produce, from pro, before -I- ducere, to lead). Tlic fundamental property of the organic world essential in repairing losses by death and in maintaining the earth's popula- tion. Although at the outset the result of un- known causes, it consists in a sejiaration of a part of the body of an individual from the parent body; division of a one-celled organism into two; or a giving olT of an egg-cell or sperm-cell from the parent. (See Cell; JIitosls.) Reproduction and growth are insei)arable, and the former is the result of growth. As Verworn states, the gen- eral ]irocess that constitutes growth is an increase of living substance, and the essence of reproduc- tion likewise consists merely in an increase of liv- ing substance. Keproduction difl'ers from growth in that a part of the snl>stance separates from the original organism. If the quantity of the living substance increases further by growth, this re- sults in a "growth beyond the measure of the individual," and the cell must divide, i.e. repro- duce. The different forms of reproduction are: ( 1 ) Self-division, secondary forms of which are (a) fission, and (b) budding or gemmation; (2) conjugation; (3) sexual reproduction. Hkproduction by Cell Division. This is the |irimai'v mode of reproduction. While that of |>hint an<l animal cells is called 'cell division,' that of the entire one-celled plant or animal is called 'self-division.' This has been observed in the ania-ba and other Protozoa, as well as in the white corpu.scles of the blood (leucocytes). See Amceba. Fission. Many of the lower invertebrate ani- mals multiply by fission or budding. In fission the bod}', as in certain planarian and annelid worms, after having reached a certain size Init not sexual maturity by ordinary cell division, is constricted into two or more parts. Each of these several parts separates and regenerates itself into an independent perfect worm. Fis- sion or self-division occurs in fully grown ex- amples of many-celled animals, as in certain polyps and starfish. liroDiNO OR Gemmation. The process of re- producing the persons of a compound individual or colony. Buds are outgrowths of a parent person that enlarge while in connection with the parent to form a new person. In the case of budding the products are unequal. All the higher plants are produced by budding and are colonies. Among animals the process occurs in Protozoa, sponges, ccRlcnterates, polyzoans. and tunicates. According to one view the tapeworm is a colony whose parts are produced by budding : even segments or rings of an annelid have been considered as produced by Viudding. Indeed, as there is no shari> line drawn between growth of the simple individual and growth of a compound REPRODUCTION, individual, so no sliarp line exists between ordi- narv development and budding; nor is there any definite distinction between cell division and di- vision in the ama'ba, and budding. This is seen in exanqdes of terminal budding, when the buds apjicar at the end of the main axis of the parent organism, as in plants and certain Protozoa and low nuilticellular animals. . Conjugation. Tlumgh aij anticipation of sex- ual rejjroduction, conjugation radically differs from it in the fact that two conjugating bodies are each an entire plant or ani- mal. It occurs in the unicellular plants, such as diatoms and desmids, and in the Infusoria. Thus in the act of conjugation of a monad-like form (Heteromita) a free-swimming individual approaches an anchored form, the posterior ends coming in contact; they then fuse like two drops of syrup, the nuclei sharing in the fusion. The product swims around freely, then rests, loses its flagella, and becomes encysted, then bursts open at three angles of the cys"t, pouring out a swarm of spores as the result of multiple internal fis- sion. It is usually among the Infusoria a tem- porary process, but in Vorticella the fusion is permanent. The result of conjugation upon the species is to prevent its deterioration. It is a process of rejuvenation, comparable with the in- tercrossing of higher plants and animals. Sexual Reproduction. In the process, some- times called 'amphigony,' of reproduction by means of sexual cells, two animals, the male and female, secrete in reproductive glands, one eggs, the other spermatozoa, the result be- ing their union and the formation of a new individual. Here still more than in conjugation sexual reproduction results in a complete renewal or rejuvenescence of the organism. In those plants and animals which also reproduce by budding sexual reproduction arrests degeneration bj' the introduction of new blood. Sexual rcpro<luction in animals is essen- tially the same in all classes above the Protozoa. There is a series of developmental processes em- braced under the following heads: (1) Matura- tion of the egg; (2) the process of fertilization; (3) a process of cleavage or .segmentation of the yolk (see Mitosis) ; and (4) formation of the three germ layers. (See EMnRYOLOGY.) The essential phenomenon in the reproduction of the many-celled animals, i.e. all above the Protozoa, is the act of fertilization or impregnation of the egg. This is elTected by the entrance of a single spermatozoiin into the egg. After the spermato- zoon has entered the egg the head and middle ■portion, which contains the body called the crn- trosome, can still be recognized as the chromatic and achromatic parts of the spermatozoon or sperm nucleus ( male pronucleus ) . In the pro- toplasm of the egg (that enveloping the nucleus and called cytoplasm) the centrosome of the sperm nucleus gives rise to rays forming 'asters.' (See Mitosis.) Preceded by these rays, the sperm nucleus travels toward the egg nucleus until it reaches and fuses with it to form a single cleavage nucleus. Then the centrosome divides into two, which migrate to opposite poles of the nucleus, while the cleavage nucleus changes to a cleavage spindle, which divides and thus initiates the embryonic development, the process being called cleavage or segmentation, At this point fertilization is complete (Hertwig). It also appears that of the chromatin particles