U76 GLOSSARr 



REALISATOBSYSTEM - pertaining to the non-apeolflc complexity of the netabollsa-apparatiis which guarantees 

 the normal course of determination ahd topogenetlc transformations In a blastema. (Lehmann.) (See 

 determination. ) 



EEALIZATION FACTOE - factor Involved In the achievement of a certain end organ production, often associ- 

 ated with the establishment of a gradient. 



EECOHSTITUTION - an aspect of regeneration where a new organ Is formed within old tissues rather than by 

 regeneration from a cut surface. A re-arrangement of parts to give new form, particularly In hydrold 

 experiments (see blastema). 



EgCOVEKf, DIFFERENTIAL - differential acclimatization In a gradient system where a low concentration of 

 depressants Indicates that regions of highest activity show greatest powers of adjustnent. 



RECUPEEATION - the reappearance of competence at a late stage In development (e.g., limb or tall blastema 

 cells). 



BEDIFFEEENTIATION - secondary differentiation within the area delimited by the term modulation. (Kaaahara, 

 1955: Arch. f. Exp. Zexi. 18). A return to a position of greater specialization In actual and 

 potential functlonu (Bloom, 193?: Physiol. Eev. 17). 



REDUPLICATION - double or even treble growths (e.g., limbs) connected with one another at some point 

 along their length, the reduplicated member being (usually) a mirror Image of the original (see 

 Bateson's Rule). 



REGENE3?ATI0N - repair or replacement of lost part or parts by growth and differentiation past the phase 

 of primordial development. The vast organizing potencies of the different regions of the early 

 embryo are lost after the completion of development and there remain only certain regions of the 

 body which are said to be capable of regeneration. Regenerative powers are more extensive among 

 embryos and adults of phyletlcally low forms. 



REGENERATION, BIAXIAL - regeneration which leads to two apical or two basal regions, accomplished In a 

 form like Planaria by cutting off the head and splitting the body from the anterior cut surface, 

 or from the posterior. The latter procedure will often give rise to a crotch head. 



REGENERATION, PHYSIOLOGICAL - changes which occur as a part of the life cycle of the organism. 



REGENERATION, RESTORATIVE - changes occurring in regular fashion after an accident, bringing about a re- 

 placement of lost or damaged parts. 



REGENERATION, WOLFFIAN - appearance of a new_ lens in the eye after removal of the former lens, due to 

 possible regeneration from the upper margin of the iris. 



REGENERATIVE CAPACITY - the ability to replace lost parts, the ability which varies (generally) inverse- 

 ly with the scale of degree of development. 



REGION, PRESUMPTIVE - regions of the blastula which, by previous experimentation, have been demonstrated 

 to develop In certain specific directions luider normal ontogenetic conditions (e.g., presumptive 

 notochord or lens). Not as definite as anlage. 



REGULATION - a reorganization toward the whole; the power of pre-gastrula embryos to utilize materials 

 remaining, after partial excision, to bring about normal conditions in respect to the relation of 

 parts; somewhat comparable to regeneration of later stages, but more flexible and more extensive 

 in early development. Ability to adjust to a strange environment and yet to develop along lines 

 of normal development. 



REINTEGRATION - the restoration to the organism, after the period of self differentiation and through 

 the action of hormonal and neural factors, of control by its Individuation field. 



RESONANCE THEORY OF REFLEX ACTIVITY - the central nervous system can emit different forms of excitation 

 and a specific muscle will respond only to that excitation appropriate to it. Rather than differ- 

 ent conducting pathways for the central nervous system and peripheral end organs (e.g., limbs), all 

 components of an excitation are transmitted to all muscles, but only that muscle, for which a 

 specific component is contained, will respond. Each muscle has motor neurones which act as selec- 

 tive transmitters. This Is the explanation (Weiss, 1936: Biol. Rev. 2:h6h) for the simultaneous 

 movement of homologous muscles even though transplanted limbs may be supplied by non- homologous 

 nerves. (See function, homologous.) 



RESPONSE, HOMOLOGOUS - an extra (transplanted) muscle is made to act by the central nervous system to- 

 gether with the normal muscle of the same name. 



REUNITION - reassembling of parts of an organism Into a functional whole (e.g., sponges as Microclona) 

 after separation of component parts. 



RICHTUNGSPOLARITAT - (German) polarity of direction, orientation of particles toward the animal or the 

 vegetal pole, but found throughout the ovum. 



ROHON-BEARD CELLS - giant ganglion cells in the spinal cord, derived from the trunk neural folds, and 

 which form the sensory pathway Including that of the peripheral sensory nerves. They have large 

 rounded nuclei and a considerable amount of cytoplasm which stains differentially with Heidenhain's 

 modification of Mallory. They are never found in the ventral part of the cord. They are associated 

 with that sensory area which is functional during the flexure of the tall following tactile stimula- 

 tion. 



BHYTHM, METACHRONAL - sequential contraction (cilia or muscle). 



EHYTB1, SYNCHRONAL - simultaneous contraction (cilia or muscle). 



SACH'S LAW - successive divisions tend to occur at right angles to each other, due to the position of 



the previously formed centrosomes. (See Hertwlg's Laws.) 

 SECTION - thin (microscopic) slice In any of several possible planes, achieved with a microtome or 



razor blade. 



