266 GLOSSARY OF EMBRYOLOGICAL TERMS 



Branchiomery — type of serial metamerism involving respiratory structures 

 exemplified by visceral arches. 



Bud — undeveloped branch, generally an anlage of an appendage (e.g., limb 

 or wing bud). 



Budding — reproductive process by which a small secondary part is pro- 

 duced from parent organism, and which gradually grows to inde- 

 pendence. 



Bulbus Arteriosus — most anterior division of early, tubular, embryonic 

 heart which leads from ventricle to truncus arteriosus. 



Cardinal Veins — anterior, posterior, and sub-cardinal veins; anterior veins 

 receive blood from head, including first three segmental veins; posterior 

 veins receive blood from all pairs of trunk segmental veins and from 

 veins of Wolffian bodies; paired cardinals enlarge and fuse, left half 

 degenerates, and balance fuses with developing inferior (posterior) 

 vena cava. 



Cell — protoplasmic territory under control of a single nucleus, whether or 

 not territory is bounded by a discrete membrane. By this definition a 

 syncytium is made up of many cells with physiological rather than 

 morphological boundaries. 



Cell Lineage — study of origin and fate of specific blastomeres in embryonic 

 development. (Syn., cytogeny.) 



Cell Theory — body of any living organism is composed of structural and 

 functional units, the primary agents of organization called cells. Each 

 cell consists of a nucleus and its sphere of influence, including the 

 cytoplasm, generally circumscribed by a membrane. "Omnis cellula e 

 cellula" (Virchow). 



Central Canal — See Neurocoel. 



Centriole — granular core of centrosome. 



Centrosome — granule (centriole) and surrounding sphere of rays (cen- 

 trosphere) which function as kinetic centers in mitosis. Center of aster 

 which does not disappear when astral rays disappear. Dynamic cen- 

 ter of mitosis. 



Centrosphere — rayed portion of centrosome; structure in spermatid which 

 gives rise to acrosome. (Syn., spermatosphere, idiosome, attraction 

 sphere. ) 



Cephalic Flexure — ventral bending of embryonic head at level of midbrain 

 and hindbrain. 



