Mr. A. Hancock on the Anatomy of Oithona. 301 



EXPLANATION OF PLATES IX. AND X. 

 Plate IX. 



Fig. 1. Side view of Oithona nobilis : — a, penis partially exserted; b, orifice 



leading to the female and androgynous parts. 

 Fig, 2. Dorsal view of the same, the papillae of one side being removed : — 



a, anal tube ; b, small orifice at the base of the same, supposed to 

 lead to a renal organ ; c, heart ; d, great efferent or branchio-car- 

 diac vessel, raised above the general surface ; e, small efferent ves- 

 sels, likewise raised above the surface, leading from the papillae to 

 the same. 



Fig. 3. Two of the papillae enlarged : — a, small efferent vessel leading to the 

 great median trunk ; b, puckered, membranous fringe with efferent 

 vessel running up its margin. 



Fig . 4 . Upper view of the buccal organ : — a, anterior extremity leading to the 

 channel of the mouth ; b, gullet ; c, c, horny jaws ; d, d, muscles 

 for advancing the whole apparatus. 



Fig. 5. Side view of buccal organ: — a, anterior extremity; b, gullet; c, horny 

 jaw; d, muscles for advancing the buccal organ. 



Fig. 6. Side view of the tongue : — o, anterior extremity. 



Fig. 7. Salivary glands ; the buccal organ and all the viscera having been 

 removed : — a, oral opening ; b, walls of the channel leading to the 

 buccal organ ; c, c, salivary glands ; d, d, ducts of the same pass- 

 ing into the wall of the channel of the mouth. 



Plate X. 



Fig. 1. General view of the viscera seen from above : — a, buccal organ; 



b, gullet ; c, stomach ; d, intestine ; e, e, hepatic ducts leading 

 from the great lateral hepatic channels within the skin ; /, one of 

 these channels laid open, exhibiting the canals from the papillae 

 opening into the same ; g, g, folliculated glandular bodies in con- 

 nexion with the anterior portions of the great hepatic channels ; 

 h, gland-like substance in connexion with the hepatic channels in 

 the skin ; i, some of these channels laid open ; j, a portion of the 

 right salivary gland ; k, penis ; Z, testis ; m, ovary ; n, n, n', mu- 

 cous gland in connexion with the female channel; o, o, peri- 

 cardial cavity seen in section ; o', o', floor of the same ; p, ven- 

 tricle ; q, auricle ; q', portion of the same attached to the great 

 efferent vessel in the skin ; r, r, the great efferent vessel seen 

 in section ; s, portal heart, opening through the floor of the peri- 

 cardium ; t, orifice supposed to be in connexion with a renal organ, 

 and opening externally by the side of the anal tube ; u, cerebral 

 ganglions. 



Fig. 2. Reproductive organs separated from the rest of the viscera and 

 spread out : — a, intromittent organ retracted ; b, testis ; c, vas de- 

 ferens ; d, duct leading from the testis to the oviduct ; e, ovary ; 

 /, duct leaving the same ; g, dilated portion of the oviduct ; 

 h, constricted portion of the same ; i, the point where it receives 

 the duct from the testis ; j, spermatheca ; k, duct from the same 

 leading to the oviduct ; I, female channel leading to external ori- 

 fice ; m, vagina or copulatory channel leading from external orifice 

 to oviduct and spermatheca ; n, n, n\ mucus-gland in connexion 

 with the female channel. 



Fig. 3. View of the heart, the pericardium being laid open : — a, ventricle ; 

 b, aorta, passing from the front of the same ; c, auricle ; d, great 

 median efferent or branchio-cardiac vessel laid open, showing its 



