390 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



gc = non-cellular core of the ganglion. 

 gs = space in which the ganglion lies. 



h = disk-like enlargement of the neural end of d. 

 hz = membrane around h. 



i = intermediate cell, or cells, of the retina. 



j = rupture in neural membrane. 



k ectoderm. 

 k' = wall of branchial or peribranchial chamber. 



1 = lacunar canal in the immature ganglion. 



I' communication between / and the space in which the ganglion lies. 

 n = nerve. 



nc = large ganglion cells in the zone of origin of the nerves. 

 oc = optic chamber. 

 on = optic nerve. 



on' fibers of the optic nerve which innervate e' . 

 on" = fibers of the optic nerve which innervate e" . 

 on'" fibers of the optic nerve which innervate e'" ' . 

 os = optic sheath . 



P = pigment cell, or pigment layer. 

 P' pigment cell, or pigment layer of e' . 

 P" pigment cell, or pigment layer of e" . 

 p'" pigment cell, or pigment layer of e'" . 

 ph.b = peripharangeal band. 

 px = pigment cells or pigment layer of ex. 

 q = spindle-shaped cells binding e'" to e" . 

 r = thick- walled portion of rod cell. 

 r' = thick-walled portion of rod cell of e' . 

 r" = thick-walled portion of rod cell of ". 

 r"' = thick-walled portion of rod cell of e'" . 

 s = thin- walled portion of rod cell. 

 6-' = thin- walled portion of rod cell of e' . 

 s" thin- walled portion of rod cell of e" . 

 s'" = thin- walled portion of rod cell of e'". 

 t tunic. 



tc = cavity between the tunic and the optic sheath . 



tn = tentacle beneath the ciliated funnel of Salpa democratica-mucronata, pro- 

 jecting into the pharyngeal cavity. 



u = greatly developed epithelial lining of the dorsal wall of h. 

 up = unpigmented spot . 



v antero-ventral process from the ganglion. 

 vl = ventro-lateral masses of rod-like, thick-walled cells. 

 w slightly developed epithelial lining of the ventral and lateral walls of //. 

 y = lateral mass of rod-like, thick-walled cells. 



2 = neural membrane. 



z' = membrane separating the optic chamber from the space in which the gan- 

 glion lies. 



The orientation of the figures is indicated by the following signs : 



> : the arrow points anteriorly. 



o : the club-shaped rod points dorsally. 



The two are often combined in this way U- 



All figures are drawn with the camera and reduced one-half, linear measurement. 



