GLOSSARY 



469 



deutoplasm, cytoplasm, 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 EMBRYO - a line representing 

 the antero-posterior axis of the future em- 

 bryo. 



BAHNUNG - 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. 

 tigrinum. ) 



BALFOUR'S LAW - the intervals between cleav- 

 ages are longer the more yolk a cell con- 

 tains in proportion to its protoplasm. "The 

 velocity of segmentation in any part of the 

 ovum is, roughly speaking, proportional 

 to the concentration of the protoplasm 

 there; and the size of the segments is in- 

 versely proportional to the concentration 

 of the protoplasm. " (Balfour - "Compara- 

 tive Embryology). 



BARFUTH'S RULE - when oblique cuts are 

 made on amphibian tails, the axis of the 

 regenerated tail will be at first perpendicu- 

 lar to the cut surface (Barfuth, 1891). 



BATESON'S RULE - (a) The long axes of re- 

 duplicated structures lie in the same plane, 

 (b) Two reduplicated limbs are mirror 

 images of each other about a plane which 

 bisects the angle between the long axes of 

 the members, and which is at right angles 

 to the plane of these axes. 



BASOPHIL - cell constituents having an affinity 

 for basic dyes, often used as an adjective 

 for an entire cell. (See acidophil) 



BAUCHSTUCK - that portion of the amphibian 



gastrula (i. e. , the ventral half) from which 

 all the organizer area has been removed, 

 thus preventing the formation of any neural 

 axis. 



BEDEUTUNGSFREMDE SELBSTDIFFEREN- 



ZIERUNG - self-differentiation independent 

 of the original presumptive fate or the pre- 

 sumed fate, implied by the new environment. 

 Neither selfwise nor neighborwise. 



BIDDER'S ORGAN - anterior portion of the 



gonad which is ovarian in character, devel- 

 oping from part of the rudiment consisting 

 wholly of cortex. A structure indicating 

 failure of medullary substance to diffuse to 

 the anterior extremity of the gonad rudi- 

 ment, found most frequently in male toads. 



BIO-ELECTRIC CURRENT - an electrical poten- 

 tial characteristic of life, disappearing upon 

 death, associated with activities of muscle, 

 nerve, secretion, and early embryos. 



BIOGENETIC LAW - ontogeny is a recapitula- 

 tion of the early development of ancestral 

 phylogeny. Embryos of higher forms re- 

 semble the embryos of lower forms in cer- 

 tain respects but they are never like the 

 adults of the lower (or ancestral) forms. 

 Not to be confused with the recapitulation 

 theory. 



BIOLOGICAL MEMORY - ontogenetic unfolding 

 of anlagen phyletically accumulated. 



BIOLOGICAL INTEGRATION - correlation of 

 parts through neural or humoral (or both) 

 influences, acquired during development. 



BIOLOGICAL ORDER - fundamental basis of 

 experimental studies, the conformity of 

 biological processes to causal postulates. 



BIORGAN - an organ in the physiological rather 

 than the morphological sense. 



BIOTONUS - the ratio between assimilation and 

 dissimilation, A/D ratio (Verworn). 



BLASTEMA - an indifferent group of cells about 

 to be organized into definite tissues, kept 

 together by the ectoplasmic matrix of the 

 constituent cells. Considered to be prim- 

 itive, embryonic, relatively undifferentia- 

 ted regenerating cell masses. Thought by 

 some to be produced by reserve cells which 

 were arrested during earlier embryonic 

 development. 



BLASTEMFELD - unitary field-like structure 

 (or functional state) without an anlage. 

 Primordial fields present in the egg stage, 

 and other fields activated only by the proc- 

 esses of induction during developnnent 

 (Lehmann). 



BLASTOCOEL - cavity of the blastula. Syn. , 

 segmentation or subgerminal cavity. 



BLASTODERM - "Because the embryo chooses 

 this as its seat and its domicile, contrib- 

 uting much to its configuration out of its 

 own substance, therefore, in the future, 

 we shall call it blastoderm." (Plander, 

 1817). 



BLASTOKINESIS - a reversal of the cephalo- 

 caudal axis in an egg, often accomplished 

 by movement during early development 

 (e. g. , insects). Syn. , revolution. 



BLASTOMERE - one of the cells of the early 

 cleavage of an egg. When there is a dis- 

 crepancy in size the smaller blastomere is 

 a micromere; the intermediate one is a 

 mesomere; and the larger one is a macro- 

 mere, but all are blastomeres. 



BLASTOPORE - the opening of the archenteron 

 (gastrocoel) to the exterior, occluded by 

 the yolk plug in amphibian embryos; con- 

 sisting of a slit-like space between the 

 elevated margin of the blastoderm and the 

 underlying yolk of the chick blastoderm; 

 and represented in the amniota as the prim- 

 itive streak. Approximate region of the 

 future anus. 



