GLOSSARY OF EMBRYOLOGICAL TERMS 285 



Jugular Veins — veins which bring blood from head, superior or internal 

 jugular being anterior cardinal veins and inferior jugular veins growing 

 toward lower jaw and mouth from base of each ductus Cuvieri. 



Karyoplasm — protoplasm within confines of nucleus. 



Kern-Plasma Relation — ratio of amount of nuclear and of cytoplasmic 

 materials present in the cell. It seems to be a function of cleavage to 

 restore kern-plasma relation from unbalanced condition of ovum with 

 its excessive yolk and cytoplasm to new ratio of gastrula or somatic 

 cell. 



Lamina Terminalis — point of suture of anterior neural folds (i.e., anterior 

 neuropore) where they are finally separated from head ectoderm; it 

 consists of a median ventral thickening at anterior limit of telen- 

 cephalon (from anterior side of optic recess to beginning of velum 

 transversum) and includes anterior commissure of torus transversus. 



Larva — stage in development when organism has emerged from its mem- 

 branes and is able to lead an independent existence, but may not have 

 completed its development. Generally (except in cases of neoteny or 

 paedogenesis) larvae cannot reproduce. 



Larynx — anterior part of original laryngo-tracheal groove which becomes 

 a tube opening into pharynx by way of glottis. 



Lateral — either right (dextral) or left (sinistral) side; laterad means toward 

 the side. 



Lateral Line Organs (or System) — line of sensory structures along side 

 of body of fishes and amphibia, generally embedded in skin and in- 

 nervated by a branch from vagus ganglion, presumably concerned 

 with recognition of low vibrations in water. Appears first at about 4 

 mm. stage in frog embryo. (Syn., ramus lateralis.) 



Lateral Mesocardium — septum posterior to heart extending from base of 

 each vitelline vein obliquely upward to dorso-lateral body wall, repre- 

 senting one of the three parts of septum transversum. 



Lateral Mesoderm — See Lateral Plate Mesoderm. 



Lateral Neural Folds — See Neural Fold. 



Lateral Plates or Lateral Plate Mesoderm — lateral mesoblast within which 

 body cavity (coelom and exocoel) arises. (Syn., lateral mesoderm.) 



Lateral Ventricles of the Brain — thick-walled and laterally compressed 

 cavities of prosencephalon which open into third ventricle by way 

 of foramen of Monro; walls will become cerebral hemispheres. 



