Page:The New International Encyclopædia 1st ed. v. 17.djvu/57

* KEPRODUCTION OF IDEAS. 41 REPRODUCTIVE SYSTEM. and (2) the appearance of tile eorresponding iiipiital processes. The word 're])roduelion' is mis- leading. First, becavise it ini])lies the 'reapi)ear- ance' of mental exiierienees wliidi have persisted and nave maintained their identity durinj; their abst'nee from consciousness. An examination of the processes of retention does not warrant the iniiilication. Secondly, reproduction is often posited where no explicit reference is made to a past event at all. Thirdly, a 'reproduced' linage is usually schematic: i.e. it contains only the out- lines or salient features of its covniterpart. The sole definite mcanini; left for the term 'repi'oduc- tion' is the uneijuivocal appearance of 'revived' sensations; i.e. of centrally aroused sensations which possess the function of referring directly to a definite period of past experience. Even when it is thus taken, the concept must not be con- fused with the old 'copy' theory, which made ideas weaker duplicates of sensations. The conditions under which reproduction of ideas takes place are various. In the associa- tional psychology, the single condition of repro- duction was said to be association. Ideas were 'called forth' by the magic of association. If, however, we conceive association to mean certain conscious complexes themselves, and not their cause, we cannot say that it conditions reproduc- tion. (See AssocnTiON of Ideas.) Association and reproduction will have a common cause. The 'law' of association will be, i.e., a law of repro- duction and will be stated in terms of cerebral connections. This general statement does not help us. however, to name the incentives to the reproduction of any particular set of processes, lior this, we must take into account the fimctions of attention, feeling, will, and mental constitu- tion (e.g. one is apt to 'reproduce' visual image- ry if one's attention is directed to visual things, or if one is visually minded, or if one's mood fits in with some particular scene), and the special conditions which are enumerated under associa- tion — frequency, recency, vividness, etc. — i.e. the jiroximate conditions which determine the rela- tive liability of reproduction of ideas. Finally, a comparisim of peripherally initiated sensations with the 'reproduced' sensations con- tained in imagery makes it possible to measure both the power of reproduction and the fidelity with which sensations aroused without the co- operation of the sensory organs represent their 'originals.' Bibliography. Kiilpe, Outlines of Psychology (New York, 189.5) ; Ward. Hind, N. 8., ii., iii. (London, 1893-94) : Bradley, Principles of Logic. Bk. ii. (London. 1883). See authorities referred to under JlE.MORy; Retentiojj ; Imagination; A.ssociATiox OF iDEA.s. and for reproduction as an experimental method, see Meiioky. REPRODUCTIVE SYSTEM, Comparative A.XATOMY OF. The germ ci-Us are not the only ones that are capable of increasing their num- bers. This is a common property of all body-tis- sue cells, and by virtue of this fact the number of individuals may be increased by division of the body and subsequent regeneration (q.v. ). In Infusoria no specialized reproductive organs are present. When the unicellular organism ex- ceeds its size-limit, it divides into two parts or 'daughter cells.' ( See Reproduction ; Fi.ssioN. ) Reproduction of sponges is either asexual or sex- ual. Asexual reproduction, or budding, may ooeur externally or internally. The sexual repro- duction may be hermaphroditic or dia'cinus. Ccelenterates are, for the most part, .sexually sep- arate, but some are hermaphrodites, as t'teno- phora. There are no organs for the transmission of the sexual jjroduets to the exterior. Sexual ducts occur for the first lime in Hat- worms. In some the entire ovary produces eggs, while in other forms a jiart of "the ovarian cell only produces egg cells an<l the rest, the 'vilel- laria,' is so modified that it pro<Uices only yolk. Both the female and the male glands communi- cate with the exterior by duets leading to the copulatory apparatus. T'lie sexes are almost al- ways separate in echinoderms. In one gioup (Synapta) of the holothurians hermaphroditism is frequent. There arc no copulatory organs nor accessory glands. The general <ugans of starli-hes develop in five pairs of bundles. One pair lies in each arm and each pair opens dorsally to the exterior by a separate opening. In the mollusks the generative apparatus is composed of germ glands, ducts, and eo])ulatory organs. The sexes are separate throughout the whole phylum. Hermaphroditism is, how- ever, wide-spread. In nearly all eases of hermaphroditism both kinds of sexual prod- ucts are produced in the same gland. The gonads either have separate ducts or utilize the nephridia. The genital glands open either (I) into the pericardium, (2) into some part of the kidney or uterus, (3J into the cloaca, or (4) di- rectly to the exterior. When there are separate duets they may be very complicated in structure. The structure of the copulatory organ and the form of the ducts with their accessory glands and tuliules vary much in detail in the different species. The sexes are distinct in many of the annelids, but Hirudinea, 01igocha?ta. and some others are exceptions. The sexes of Polychseta are separate with a very few exceptions. The ovaries or testes are segmentally repeated sev- eral or many times. The ripe eggs and sperm float in the coelomic cavity, to be picked up and discharged to the exterior by the nephridia, or by nephridia specially modified into genital ducts. The sexes are .separate in Crustacea except in a few cases. The male and female sexual glands are constructed on the same plan and have a similar position in the body. There is only one pair, and in certain species only one gland. The parts that make up the sexual apparatus are as follows: (1) The genital organs (ovaries and testes); (2) ducts (oviducts, vasa deferentia); (3) terminal jiarts (vulva, vagina, and recepta- culum seminis iu the female, and ductus ejacula- torus in the male) ; (4) outer copulatory organs. Except in Cladocera and some Copcpoda the geni- tal apertures arc situated on the ventral side. In all hexapods they open at the end of the abdo- men. In certain species there are glands whose secretion unites the sperm cells into capsules or spermatophores. A penis may also be present. The female apparatus may possess a receptacle for the penis and another for storing the sperm. The testis and ovaries consist of a varying num- ber of long tubes which together enter the vas deferens or oviduct. The ovarian tubes are of two kinds, those with and those without nutri- tive cells. The nutritive cells may alternate with the egg cells or they may be collected in a bunch and furnish nutritive material to the egg cells by means of fine constricting strands. Coming to