DESCRIPTION OF PLATES. 
Reference Letters. 
A.B.S. = Achetous body seg- 
ment. 
Ac. = Aciculum. 
adler, = Acrosome or apical body 
of spermatozoon. 
An. = Anus. 
Ant.L. = Anterior lobe of brain. 
Ale, = TOP UN BOE 
B. = Blastophore (residual mass 
of protoplasm). 
Bl. V. = Blood vessel. 
Br. = Gill. 
br. Aff ) = Afferent and efferent 
Br.Lf. 3 
br. and N.Aff. = Afferent vessel 
to gill and nephridium. 
branchial vessels. 
B.Sh, = Sheath formed of buccal 
muscles. 
Bucc.M. = Buccal mass. 
Bucc.Pap. = Papille of buccal 
mass. 
Caud.Sep. = Caudal septum. 
Ch. Seg.= Cheetigerous segment. 
Chi.Gr. = Chlorogogen granules. 
Chl. Tiss. = Chlorogogenous tissue. 
Cel. = Coeelom. : 
Cal. Hpith. = Coelomic epithelium. 
Conn. Tiss. = Connective tissue. 
Cut. = Cuticle. 
Diat. = Diatom (as otolith). 
D.L.V. = Dorsal longitudinal 
vessel. 
D.Mes, = Dorsal mesentery. 
Dphm. = Diaphragm. 
Dphm.P. = Pouch of first dia- 
phragm. 
D.V. = Dorsal vessel, 
Hndth.N. = Nucleus of endo- 
thelium. 
Hip. = Epidermis. i 
Hac.Gr. = Exeretory granules. 
Het.Op.Ot. = External opening 
of otocyst. 
Gang.C. = Ganglion cell. 
Gast.Lat. = Lateral 
vessel. 
gastric 
G.C. = Giant nerve cell. 
G.F’. = Giant nerve fibre. 
Gl.¢. = Gland cell. 
Gon, = Gonad. 
Gon.V. = Gonidial vessel. 
Ht.B. = Heart body. 
Int.V. = Intestinal vessel. 
M.Circ. = Cireular muscles. 
Met.Gr. = Metastomial groove. 
Mid.Com. = Middle commissure 
of brain. 
M. Long. = Longitudinal muscles. 
Mo. = Mouth. 
M.Obl. = Oblique muscles. 
M.P. = Middle piece of sperma- 
tozoon. 
Musc. = Muscles. 
N. = Nucleus. 
N.Aff. = Nephridial afferent 
vessel. 
N.C. = Nerve cord. 
N.EHp. = Nerve to epidermis. 
Nfb. = Neurofibrille. 
Ngl. = Neurogha. 
Nim. = Neurilemma. 
N.L.V. =Nephridal longitudinal 
vessel. 
Nm. = Neuropodium. 
