GLOSSARY 1+55 



.ANDEO-MEBOGONES - egg fragmenta developing with the sperm nucleus only, achieved either through surgical 



removal of the egg nucleus and some cytoplasm; by constricting the pro-nuclei apart prior to syngamy; 



or by centrlfuging the pro-nuclei apart. 

 ANEUPLOIDY - deviation from normal diploidy but involving partial sets of chromosomes (Tackhohn, 1922). 

 ANEUPLOIDY, MULTIFOBM - complex chromosomal mosaics, possibly the result of multipolar mitoses (Book, 194U) 

 ANEUBOGENIC - used in relation to organs developed vithout proper components of the central nervous system 



(e.g., limb buds in embryos without spinal cords). 

 ANEMTEFION - formation and constriction of archenteron by evagination instead of invagination, following 



the application of heat (Driesch, I895). 

 ANGENESIS - regeneration of tissues. 

 ANLAGE - a rudiment; a group of cells which indicate a prospective development into a part or organ. 



Syn., ebauch^ or primordium. 

 ANIMALIZATION - changing by physical or chemical means the presumptive fate of embryonic areas which 



normally would have become endodermal. Syn., ectodermlzation, or animal! si erxuig of Lindahl. 

 ANOEMOGENESE - a course of development which deviates in a typical manner from the normal (Lehmann). 

 ANTEEIOE - toward the head; head end. Syn., cephalic, cranial, rostral. 

 APEOSOMUS - featureless face due to the arrest of development, the skin covering normal but lacking in 



eyes, nose, and mouth. 

 AECHENCEPHALON - anterior portion of the brain which gives rise to the telencephalon and the dlencephalon; 



pre-chordal brain. 

 AECHIPLASM - specific material which gives rise to the asters and spindle (Boveri). 

 AEEA - a morphogenetic cell group representing one of the constituent regions of a fate-map, generally of 



a blastula stage or later. 

 ABEAL - first an invisible, then a sharply differentiated region of the blastema, out of which develops a 



primitive organ; the organ arising from the blastema through segregation, ( organogenetlsches of 



Lehmann) . 

 AREA OPACA - the marginal ring or extra-embryonic blaBtoderm of the chick embryo around the area pellu- 



cida, opaque because of direct contact with the underlying yolk. 

 AEEA PELLUCIDA - the central portion of the chick blastoderm from which the embryo is developed, pellucid 



because it la lifted off of the underlying yolk, providing a space beneath the blastoderm through 



which light can be transmitted. 

 AEEA VASCULOSA - the portion of the area opaca of the chick blastoderm in which the extra- embryonic blood 



vessels will develop. 

 AEEA VITELLINA - the portion of the area opaca of the chick blastoderm peripheral to the area vasculosa. 

 ARHHENOKAEYOTIC - refers to a blastomere of the normally fertilized egg where there has been a separation 



of the nuclear components; or in cases of dispemy, where the haploid chromosomes from the single 



sperm are isolated in the blastomere. 

 AERHENOTOKY - parthenogenetic production of males, exclusively. 

 ASSIMILATION - process of determinative incorporation of a foreign blastema into the functional status of 



the host blastema. 

 ASTEE - the "atar-shaped structure" aurroundlng the centrosome ( Fol, 1877); lines radiating in all direc- 

 tions from the centrosome during mitosis. 

 ASTCMUS - complete lack or atresia of the mouth. 

 ASYNTAXIA DOESALIS - failure of the neural tube to close. 

 ATELIOTIC - arrested development of the skeleton due to non-union of the epiphyses, characteristic of 



some dwarfs . 

 ATOKUS - without offspring. 

 ATTRACTION, NON-SPECIFIC - attraction of nerve fibers toward any structure in the vicinity, (e.g., graft 



rudiments of chick embryos such as brain tissue, if placed on the chorlo-allantois, will often send 



out nerve fibers toward the nearby muscle segments, a situation that would not occur under normal 



conditions) . 

 AUFLAGERUNG - the placing of competent or responsive ectoderm on a dead inductor in order to test the in- 

 ductive power of the latter. 

 AUTOGAMY - self-fertilization. 



AUTOPARTHENOGENESIS - parthenogenetic stimulation of eggs to develop by materials from other eggs. 

 AUXESIS - growth by cell expansion but without cell division. 



AXIS - central or median line. The egg axis takes into account the concentration of deutoplasm, cyto- 

 plasm, and the position of the nucleus, so that the egg axis and egg polarity are essentially the 



same. 

 AXIS OF THE CELL - a line passing through the centrosome and nucleus of the cell. 

 AXIS OF THE IMBFYO - a line representing the antero-posterlor axis of the future embiyo. 



BAHNUTJG - competence or labile determination (Vogt, 1928). 



BALANCER - cylindrical and paired projections of ectoderm with mesenchymatous cores, used as tactile and 

 balancing organs by some urodeles in the place of (anuran) suckers. (Rudimentary or absent in 

 A. tigrlnxm. ) 



BALFOUE'S LAW - the intervals between cleavages are longer the more yolk a cell contains in proportion to 

 its protoplasm. "The velocity of aegmentation in any part of the ovum is, roughly speaking, propor- 

 tional to the concentration of the protoplasm there; and the size of the segments is inversely pro- 

 portional to the concentration of the protoplasm." (Balfour - "Comparative Embryology). 



